fix parsing links as mentions

lib/helpers/extensions/join_room_with_snackbars.dart

@@ -12,7 +12,7 @@ extension JoinRoomWithSnackbars on ClientController {
     String roomAlias,
     WidgetRef ref,
   ) async {
-    final roomIdOrAlias = roomAlias.mention;
+    final roomIdOrAlias = roomAlias.mention ?? roomAlias;
     // TODO: Parse vias properly
 
     final scaffoldMessenger = ScaffoldMessenger.of(context);

lib/helpers/extensions/link_to_mention.dart

@@ -9,7 +9,7 @@ extension LinkToMention on String {
   ///
   /// Returns the decoded identifier (e.g. "#room:matrix.org")
   /// or null if this is not a Matrix link.
-  String get mention {
+  String? get mention {
     final trimmed = trim();
 
     final matrixTo = RegExp(
@@ -39,6 +39,6 @@ extension LinkToMention on String {
       } catch (_) {}
     }
 
-    return this;
+    return null;
   }
 }

lib/widgets/chat_page/html/mention_chip.dart

@@ -10,9 +10,9 @@ class MentionChip extends ConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final membership = content.mention.startsWith("@") == true
+    final membership = content.mention!.startsWith("@") == true
         ? ref
-              .watch(UserController.provider(content.mention))
+              .watch(UserController.provider(content.mention!))
               .whenOrNull(data: (data) => data)
         : null;
 
@@ -30,7 +30,7 @@ class MentionChip extends ConsumerWidget {
         child: Chip(
           label: Text(
             (membership == null ? null : "@${membership.displayName}") ??
-                content.mention,
+                content.mention!,
             style: TextStyle(
               fontWeight: FontWeight.bold,
               color: Theme.of(context).colorScheme.onPrimary,