Bug 409591. Thunderbird: newsgroup/feed messages blank in virtual buffer. Correct the previous checkin for this bug which caused bug 414574. r=surkov, sr=bz, a=blocking1.9

accessible/src/base/nsDocAccessible.cpp

@@ -697,7 +697,8 @@ nsresult nsDocAccessible::RemoveEventListeners()
   if (rootAccessible) {
     nsRefPtr<nsCaretAccessible> caretAccessible = rootAccessible->GetCaretAccessible();
     if (caretAccessible) {
-      nsCOMPtr<nsIPresShell> presShell(GetPresShell());
+      // Don't use GetPresShell() which can call Shutdown() if it sees dead pres shell
+      nsCOMPtr<nsIPresShell> presShell(do_QueryReferent(mWeakShell));
       caretAccessible->RemoveDocSelectionListener(presShell);
     }
   }