home [nfc]: Comment with issue number on an incorrect !

Related: zulip#1219

Author: chrisbobbe

lib/widgets/home.dart

@@ -181,6 +181,7 @@ class _LoadingPlaceholderPageState extends State<_LoadingPlaceholderPage> {
   Widget build(BuildContext context) {
     final zulipLocalizations = ZulipLocalizations.of(context);
     final realmUrl = GlobalStoreWidget.of(context)
+      // TODO(#1219) `!` is incorrect
       .getAccount(widget.accountId)!.realmUrl;
 
     return Scaffold(