After passing from 1.653 to 2.1 unable to apply or to save a new System Configuration
And in the system logs I found:

May 04, 2016 7:48:54 PM INFO org.eclipse.jetty.util.log.JavaUtilLog info

Started w.@7b7117d8

{/,file:/var/cache/jenkins/war/,AVAILABLE} {/var/cache/jenkins/war}

May 04, 2016 7:48:54 PM INFO org.eclipse.jetty.util.log.JavaUtilLog info

Started ServerConnector@3c3a15bb

{HTTP/1.1} {0.0.0.0:8080}

May 04, 2016 7:48:54 PM INFO org.eclipse.jetty.util.log.JavaUtilLog info

Started @1026ms

May 04, 2016 7:48:54 PM INFO winstone.Logger logInternal

Winstone Servlet Engine v2.0 running: controlPort=disabled

May 04, 2016 7:48:54 PM INFO jenkins.InitReactorRunner$1 onAttained

Started initialization

May 04, 2016 7:48:55 PM INFO jenkins.InitReactorRunner$1 onAttained

Listed all plugins

May 04, 2016 7:48:55 PM INFO de.pellepelster.jenkins.walldisplay.WallDisplayPlugin loadConfiguration

Loaded configuration data: de.pellepelster.jenkins.walldisplay.Configuration@6dd550ab[
theme=default
jenkinsTimeOut=15
jenkinsUpdateInterval=20
showDetails=true
showGravatar=false
fontFamily=sans-serif
buildRange=all
sortOrder=job name
showWeatherReport=true
showJunitResults=true
maxQueuePositionToShow=15
gravatarUrl=http://www.gravatar.com/avatar/
]

May 04, 2016 7:48:59 PM INFO jenkins.InitReactorRunner$1 onAttained

Prepared all plugins

May 04, 2016 7:48:59 PM INFO jenkins.InitReactorRunner$1 onAttained

Started all plugins

May 04, 2016 7:48:59 PM INFO jenkins.InitReactorRunner$1 onAttained

Augmented all extensions

May 04, 2016 7:48:59 PM INFO jenkins.InitReactorRunner$1 onAttained

Loaded all jobs

May 04, 2016 7:48:59 PM INFO hudson.model.AsyncPeriodicWork$1 run

Started Download metadata

May 04, 2016 7:48:59 PM INFO hudson.model.AsyncPeriodicWork$1 run

Finished Download metadata. 2 ms

May 04, 2016 7:49:00 PM INFO org.jenkinsci.main.modules.sshd.SSHD start

Started SSHD at port 34005

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Completed initialization

May 04, 2016 7:49:00 PM INFO org.springframework.context.support.AbstractApplicationContext prepareRefresh

Refreshing org.springframework.web.context.support.StaticWebApplicationContext@7b9d65fa: display name [Root WebApplicationContext]; startup date [Wed May 04 19:49:00 CEST 2016]; root of context hierarchy

May 04, 2016 7:49:00 PM INFO org.springframework.context.support.AbstractApplicationContext obtainFreshBeanFactory

Bean factory for application context [org.springframework.web.context.support.StaticWebApplicationContext@7b9d65fa]: org.springframework.beans.factory.support.DefaultListableBeanFactory@52f4dd45

May 04, 2016 7:49:00 PM INFO org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@52f4dd45: defining beans [authenticationManager]; root of factory hierarchy

May 04, 2016 7:49:00 PM INFO org.springframework.context.support.AbstractApplicationContext prepareRefresh

Refreshing org.springframework.web.context.support.StaticWebApplicationContext@735c2129: display name [Root WebApplicationContext]; startup date [Wed May 04 19:49:00 CEST 2016]; root of context hierarchy

May 04, 2016 7:49:00 PM INFO org.springframework.context.support.AbstractApplicationContext obtainFreshBeanFactory

Bean factory for application context [org.springframework.web.context.support.StaticWebApplicationContext@735c2129]: org.springframework.beans.factory.support.DefaultListableBeanFactory@f632823

May 04, 2016 7:49:00 PM INFO org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@f632823: defining beans [filter,legacy]; root of factory hierarchy

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Started initialization

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Listed all plugins

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Prepared all plugins

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Started all plugins

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Augmented all extensions

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Loaded all jobs

May 04, 2016 7:49:00 PM INFO jenkins.InitReactorRunner$1 onAttained

Completed initialization

May 04, 2016 7:49:00 PM INFO hudson.WebAppMain$3 run

Jenkins is fully up and running

May 04, 2016 7:49:59 PM INFO hudson.model.AsyncPeriodicWork$1 run

Started Gravatar periodic lookup

May 04, 2016 7:50:02 PM INFO hudson.model.AsyncPeriodicWork$1 run

Finished Gravatar periodic lookup. 2,516 ms

May 04, 2016 7:53:20 PM WARNING org.eclipse.jetty.util.log.JavaUtilLog warn

Error while serving http://172.29.0.233:8080/configSubmit
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:320)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:163)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:96)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:124)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:746)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:876)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
at com.smartcodeltd.jenkinsci.plugin.assetbundler.filters.LessCSS.doFilter(LessCSS.java:47)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:126)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:93)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:499)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: javax.servlet.ServletException: This page expects a form submission but had only {}
at org.kohsuke.stapler.RequestImpl.getSubmittedForm(RequestImpl.java:998)
at jenkins.model.Jenkins.doConfigSubmit(Jenkins.java:3357)
... 66 more