fix: mxid validation

lib/views/invitation_selection.dart

@@ -99,11 +99,10 @@ class _InvitationSelectionState extends State<InvitationSelection> {
     }
     setState(() {
       foundProfiles = List<Profile>.from(response.results);
-      if ('@$text'.isValidMatrixId &&
+      if (text.isValidMatrixId &&
-          foundProfiles.indexWhere((profile) => '@$text' == profile.userId) ==
+          foundProfiles.indexWhere((profile) => text == profile.userId) == -1) {
-              -1) {
         setState(() => foundProfiles = [
-              Profile.fromJson({'user_id': '@$text'}),
+              Profile.fromJson({'user_id': text}),
             ]);
       }
       final participants = room

lib/views/new_private_chat.dart

@@ -51,11 +51,14 @@ class _NewPrivateChatState extends State<NewPrivateChat> {
     }
   }
 
-  void searchUserWithCoolDown(BuildContext context, String text) async {
+  void searchUserWithCoolDown(BuildContext context) async {
+    if (controller.text.startsWith('@')) {
+      controller.text = controller.text.substring(1);
+    }
     coolDown?.cancel();
     coolDown = Timer(
       Duration(seconds: 1),
-      () => searchUser(context, text),
+      () => searchUser(context, controller.text),
     );
   }
 
@@ -99,8 +102,7 @@ class _NewPrivateChatState extends State<NewPrivateChat> {
                 controller: controller,
                 autofocus: true,
                 autocorrect: false,
-                onChanged: (String text) =>
+                onChanged: (String text) => searchUserWithCoolDown(context),
-                    searchUserWithCoolDown(context, text),
                 textInputAction: TextInputAction.go,
                 onFieldSubmitted: (s) => submitAction(context),
                 validator: (value) {