Fixing an NPE in StackPanel that occurs very rarely in IE.

Patch by: jlabanca
Review by: jat (desk)



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7127 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/user/src/com/google/gwt/user/client/ui/StackPanel.java b/user/src/com/google/gwt/user/client/ui/StackPanel.java
index 64b49ef..abbb628 100644
--- a/user/src/com/google/gwt/user/client/ui/StackPanel.java
+++ b/user/src/com/google/gwt/user/client/ui/StackPanel.java
@@ -264,7 +264,7 @@
   }
 
   private int findDividerIndex(Element elem) {
-    while (elem != getElement()) {
+    while (elem != null && elem != getElement()) {
       String expando = DOM.getElementProperty(elem, "__index");
       if (expando != null) {
         // Make sure it belongs to me!