341850 Protect QTP dump from bad stacks

git-svn-id: svn+ssh://dev.eclipse.org/svnroot/rt/org.eclipse.jetty/jetty/trunk@2984 7e9141cc-0065-0410-87d8-b60c137991c4

VERSION.txt

@@ -28,6 +28,7 @@ jetty-7.4.0.RC0
  + 341736 Split jetty-nested out of war module
  + 341726 JSONPojoConverter handles characters
  + 341992 Overlayed context deployer
+ + 341850 Protect QTP dump from bad stacks
  + JETTY-1245 Pooled Buffers implementation
  + JETTY-1354 Added jetty-nested
  + Ensure generated fragment names are unique

jetty-util/src/main/java/org/eclipse/jetty/util/thread/QueuedThreadPool.java

@@ -489,7 +489,7 @@ public class QueuedThreadPool extends AbstractLifeCycle implements ThreadPool, E
             }
             else
             {
-                dump.add(thread.getId()+" "+thread.getName()+" "+thread.getState()+" @ "+trace[0]+(idle?" IDLE":""));
+                dump.add(thread.getId()+" "+thread.getName()+" "+thread.getState()+" @ "+(trace.length>0?trace[0]:"???")+(idle?" IDLE":""));
             }
         }