Use the latest api for com.sun.source.util.Trees. Reported upstream at:
http://netbeans.org/bugzilla/show_bug.cgi?id=201267

Index: netbeans/debugger.jpda.ui/src/org/netbeans/modules/debugger/jpda/ui/WatchPanel.java
===================================================================
--- netbeans.orig/debugger.jpda.ui/src/org/netbeans/modules/debugger/jpda/ui/WatchPanel.java	2011-08-23 21:25:07.276130076 +0100
+++ netbeans/debugger.jpda.ui/src/org/netbeans/modules/debugger/jpda/ui/WatchPanel.java	2011-08-23 21:25:42.546130576 +0100
@@ -43,6 +43,7 @@
  */
 package org.netbeans.modules.debugger.jpda.ui;
 
+import com.sun.source.tree.CatchTree;
 import com.sun.source.tree.ClassTree;
 import com.sun.source.tree.CompilationUnitTree;
 import com.sun.source.tree.IdentifierTree;
@@ -716,6 +717,11 @@
             return trees.getDocComment(path);
         }
 
+        @Override
+        public TypeMirror getLub(CatchTree tree) {
+            return trees.getLub(tree);
+        }
+
     }
 
     public static final class DelegatingBorder implements Border {
