Exception:
Stacktrace:

java.lang.NullPointerException
	at hudson.Util.rawEncode(Util.java:755)
	at hudson.matrix.MatrixProject.getRootDirFor(MatrixProject.java:475)
	at hudson.matrix.MatrixProject.getRootDirFor(MatrixProject.java:461)
	at hudson.matrix.MatrixProject.getRootDirFor(MatrixProject.java:90)
	at hudson.model.AbstractItem.getRootDir(AbstractItem.java:118)
	at hudson.model.Items.getConfigFile(Items.java:121)
	at hudson.model.AbstractItem.getConfigFile(AbstractItem.java:373)
	at hudson.model.AbstractItem.save(AbstractItem.java:368)
	at hudson.model.Job.save(Job.java:152)
	at hudson.matrix.MatrixProject.rebuildConfigurations(MatrixProject.java:414)
	at hudson.matrix.MatrixProject.submit(MatrixProject.java:615)
	at hudson.model.Job.doConfigSubmit(Job.java:973)
	at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:624)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:282)
	at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:149)
	at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:88)
	at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:103)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
	at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:233)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
	at org.kohsuke.stapler.Stapler.service(Stapler.java:159)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
	at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
	at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
	at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
	at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
	at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
	at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
	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:166)
	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:173)
	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:66)
	at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
	at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
	at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
	at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
	at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
	at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
	at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
	at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
	at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
	at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
	at java.lang.Thread.run(Thread.java:662)