Fixing crash in nsFocusController::GetWindowFromDocument. Patch by allan@beaufour.dk, r+sr=jst@mozilla.org, a=benjamin@smedbergs.us

dom/src/base/nsFocusController.cpp

@@ -394,7 +394,7 @@ nsFocusController::GetWindowFromDocument(nsIDOMDocument* aDocument)
   nsCOMPtr<nsPIDOMWindow> win =
     do_QueryInterface(doc->GetScriptGlobalObject());
 
-  if (win->IsInnerWindow()) {
+  if (win && win->IsInnerWindow()) {
     return win->GetOuterWindow();
   }