After the upgrade from 1.151 to 1.156 and 1.159 if found myself unable to use
the cobertura plugin.
It gives me the following stacktrace, which strangly enough refers to a problem
in hudson.tasks.MailMessageIdAction.

java.lang.AssertionError: Action hudson.tasks.MailMessageIdAction@1a9f63f
returned null from the getUrlName() method
at hudson.model.Actionable.getDynamic(Actionable.java:83)
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:585)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:103)
at org.kohsuke.stapler.MetaClass$15.dispatch(MetaClass.java:361)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:294)
at org.kohsuke.stapler.MetaClass$15.dispatch(MetaClass.java:361)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:294)
at org.kohsuke.stapler.MetaClass$9.doDispatch(MetaClass.java:240)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:294)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:231)
at org.kohsuke.stapler.Stapler.service(Stapler.java:79)
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.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:79)
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)

I'm running the cobertura plugin version ver.0.8.4.