My plugin component implementing hudson.model.Action returns null in the hope of
not being displayed in the menu. This results in a NPE. I'm pasting the first
lines of the exception and if I can find an upload box I'll give the full
stacktrace.

java.lang.NullPointerException
at java.util.regex.Matcher.getTextLength(Matcher.java:1140)
at java.util.regex.Matcher.reset(Matcher.java:291)
at java.util.regex.Matcher.<init>(Matcher.java:211)
at java.util.regex.Pattern.matcher(Pattern.java:888)
at hudson.Functions.getActionUrl(Functions.java:870)
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)