bug 441610 - Calling getAttributes() on a defunct object crashes Thunderbird, r=aaronlev

accessible/src/base/nsAccessible.cpp

@@ -2045,6 +2045,9 @@ nsAccessible::GetAttributes(nsIPersistentProperties **aAttributes)
 {
   NS_ENSURE_ARG_POINTER(aAttributes);  // In/out param. Created if necessary.
   
+  if (IsDefunct())
+    return NS_ERROR_FAILURE;
+
   nsCOMPtr<nsIContent> content = GetRoleContent(mDOMNode);
   if (!content) {
     return NS_ERROR_FAILURE;