mshtml: Don't crash in on_start_uri_open on nscontainer without associated document.

dlls/mshtml/nsio.c

@@ -222,12 +222,14 @@ nsresult on_start_uri_open(NSContainer *nscontainer, nsIURI *uri, PRBool *_retva
     }
 
     if(!wine_uri->is_doc_uri) {
+        wine_uri->is_doc_uri = TRUE;
+
         if(!wine_uri->container) {
             nsIWebBrowserChrome_AddRef(NSWBCHROME(nscontainer));
             wine_uri->container = nscontainer;
         }
 
-        wine_uri->is_doc_uri = TRUE;
+        if(nscontainer->doc)
             *_retval = translate_url(nscontainer->doc, wine_uri);
     }