Added an extension point for inserting actions across all projects without configuration.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@22262 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/Util.java

@@ -862,6 +862,10 @@ public class Util {
         return l!=null ? l : Collections.<T>emptySet();
     }
 
+    public static <T> Collection<T> fixNull(Collection<T> l) {
+        return l!=null ? l : Collections.<T>emptySet();
+    }
+
     /**
      * Cuts all the leading path portion and get just the file name.
      */