fix: suggestions menu and use empty map in html messages null return

lib/pages/chat/events/html_message.dart

@@ -95,7 +95,7 @@ class HtmlMessage extends StatelessWidget {
         final identityParts = url.parseIdentifierIntoParts();
         final identifier = identityParts?.primaryIdentifier;
         if (identifier == null) {
-          return {'': null};
+          return {};
         }
         if (identifier.sigil == '@') {
           // we have a user pill
@@ -127,13 +127,13 @@ class HtmlMessage extends StatelessWidget {
               };
             }
           }
-          return {'': null};
+          return {};
         }
         if (identifier.sigil == '!') {
           // we have a room ID pill
           final r = room.client.getRoomById(identifier);
           if (r == null) {
-            return {'': null};
+            return {};
           }
           return {
             'displayname':
@@ -141,7 +141,7 @@ class HtmlMessage extends StatelessWidget {
             'avatar_url': r.getState('m.room.avatar')?.content['url'],
           };
         }
-        return {'': null};
+        return {};
       },
     );
   }

lib/pages/chat/input_bar.dart

@@ -49,7 +49,7 @@ class InputBar extends StatelessWidget {
     }
     final searchText =
         controller!.text.substring(0, controller!.selection.baseOffset);
-    final List<Map<String, String?>> ret = <Map<String, String>>[];
+    final List<Map<String, String?>> ret = <Map<String, String?>>[];
     const maxResults = 30;
 
     final commandMatch = RegExp(r'^\/([\w]*)$').firstMatch(searchText);