message: fix formatBar not hidden after highlight-backspacing text partially
diff: @@ -447,6 +447,8 @@ export default class BasicMessageEditor extends React.Component {
  } else if (event.key === Key.TAB) {
  this._tabCompleteName();
  handled = true;
  + } else if (event.key === Key.BACKSPACE) {
  + this._formatBarRef.hide();
  }
  }
  if (handled) {
  