javax.servlet.ServletException: java.lang.IllegalArgumentException: Null value not allowed as an environment variable: M2_HOME
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:719)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
	at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:241)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:677)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
	at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:241)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:677)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:770)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:583)
	at org.kohsuke.stapler.Stapler.service(Stapler.java:214)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
	at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:598)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1367)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
	at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
	at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:206)
	at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:179)
	at net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
	at org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
	at com.marvelution.hudson.plugins.apiv2.servlet.filter.HudsonAPIV2ServletFilter.doFilter(HudsonAPIV2ServletFilter.java:115)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
	at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1338)
	at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:48)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1338)
	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 org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:124)
	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 org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:174)
	at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
	at jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:64)
	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$1.doFilter(ChainedServletFilter.java:87)
	at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
	at de.theit.jenkins.crowd.CrowdServletFilter.doFilter(CrowdServletFilter.java:195)
	at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1338)
	at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:50)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1338)
	at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1338)
	at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:484)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
	at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:499)
	at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
	at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)
	at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:413)
	at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:192)
	at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:999)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
	at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:250)
	at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:149)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
	at org.eclipse.jetty.server.Server.handle(Server.java:350)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:454)
	at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:890)
	at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:944)
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:630)
	at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:230)
	at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:77)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:620)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:46)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:603)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:538)
	at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.IllegalArgumentException: Null value not allowed as an environment variable: M2_HOME
	at hudson.EnvVars.put(EnvVars.java:172)
	at hudson.tasks.Maven$MavenInstallation.buildEnvVars(Maven.java:492)
	at hudson.maven.MavenModuleSetBuild.getEnvironment(MavenModuleSetBuild.java:173)
	at hudson.scm.SubversionSCM.getModuleRoot(SubversionSCM.java:1381)
	at hudson.model.AbstractBuild.getModuleRoot(AbstractBuild.java:379)
	at hudson.maven.MavenModuleSet.doCheckFileInWorkspace(MavenModuleSet.java:1173)
	at sun.reflect.GeneratedMethodAccessor1260.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:288)
	at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:151)
	at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:90)
	at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:111)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:677)
	... 78 more