Fix force completion and hide rooms with no alias

src/autocomplete/RoomProvider.js

@@ -44,7 +44,7 @@ export default class RoomProvider extends AutocompleteProvider {
                     ),
                     range,
                 };
-            }).slice(0, 4);
+            }).filter(completion => !!completion.completion && completion.completion.length > 0).slice(0, 4);
         }
         return completions;
     }