message: [FIX] Stop mention tracking when messagebox is empty
diff: @@ -199,6 +199,8 @@ class MessageBox extends Component {
  }
  const [, lastChar, name] = result;
  this.identifyMentionKeyword(name, lastChar);
  + } else {
  + this.stopTrackingMention();
  }
  }, 100)
  