Bug 453858 followup - quiet console warnings in nsDOMClassInfo.cpp. r+sr=bzbarsky

dom/src/base/nsDOMClassInfo.cpp

@@ -7612,7 +7612,9 @@ nsArraySH::GetItemAt(nsISupports *aNative, PRUint32 aIndex,
                      nsISupports **aResult)
 {
   nsCOMPtr<nsINodeList> list(do_QueryInterface(aNative));
-  NS_ENSURE_TRUE(list, NS_ERROR_UNEXPECTED);
+  if (!list) {
+    return NS_ERROR_UNEXPECTED;
+  }
 
   NS_IF_ADDREF(*aResult = list->GetNodeAt(aIndex));