Versions used: Hudson 1.252 (installed debian package, run as application and
not within tomcat), Violations Plugin 0.7.1, Java JDK 1.5.0_15

Since quite some time now (weeks?) we use the violations plugin 0.7.1 within
Hudson. Though once it worked (unclear since when) correctly, with the latest
version of the violations plugin (v0.7.1) we get the following error when
accessing an URL like:
(a) http://hudson-server:8080/job/HadesSite/90/violations/
(b) http://hudson-server:8080/job/HadesSite/violations/

And some of the violation trend-graphs are not created:
ad (a): for a specific build, the violation-graph IS created for single modules,
but the aggregated graph is not created
ad (b): for that link, there are NO violation-graphs at all (only the surrogate
"empty" icon indicating, that there's no image to load)

Can somebody help what is wrong here? Strange is, that it once worked.
I guess (but only guess), that maybe the reports to be aggregrated have a
changed and now inconsistent data format. We use the following hudson plugins in
the site report build process: checkstyle plugin 1.15, pmd (+cpd) plugin 1.15,
findbugs plugin 2.18

The hudson.log shows the following errors when choosing one of the above URLs
(for our internal project HadesSite):

[webapp 2008/09/23 11:52:10] - Error while serving
http://dombuilder.schlund.de:8080/job/NexDomSite/violations/graph
java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor342.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:103)
at org.kohsuke.stapler.Function.bindAndinvoke(Function.java:57)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:75)
at
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:440)
at org.kohsuke.stapler.MetaClass$15.dispatch(MetaClass.java:384)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:440)
at org.kohsuke.stapler.MetaClass$9.doDispatch(MetaClass.java:263)
at
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:440)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:361)
at org.kohsuke.stapler.Stapler.service(Stapler.java:121)
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:61)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:53)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:88)
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:595)
Caused by: java.lang.NullPointerException

[Winstone 2008/09/23 11:52:10] - Untrapped Error in Servlet
java.lang.NullPointerException

javax.servlet.ServletException
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:449)
at org.kohsuke.stapler.MetaClass$15.dispatch(MetaClass.java:384)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:440)
at org.kohsuke.stapler.MetaClass$9.doDispatch(MetaClass.java:263)
at
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:440)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:361)
at org.kohsuke.stapler.Stapler.service(Stapler.java:121)
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:61)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:53)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:88)
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:595)
#---------------

If you need more info to investigate, please let me know.

Cheers,
/Jens