bug 130894, add null checks to avoid crashes found by js debugger users.

r=caillon@returnzero.com, sr=ben, a=asa


git-svn-id: svn://10.0.0.236/trunk@116801 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/xul/base/src/nsMenuFrame.cpp

@@ -918,6 +918,12 @@ nsMenuFrame::OpenMenuInternal(PRBool aActivateFlag)
 void
 nsMenuFrame::GetMenuChildrenElement(nsIContent** aResult)
 {
+  if (!mContent)
+  {
+    *aResult = nsnull;
+    return;
+  }
+  
   nsresult rv;
   nsCOMPtr<nsIXBLService> xblService = 
            do_GetService("@mozilla.org/xbl;1", &rv);