message: Don't show FormatBar if composer is empty
diff: @@ -359,6 +359,8 @@ export default class BasicMessageEditor extends React.Component {
  }
  _onSelectionChange = () => {
  + const {isEmpty} = this.props.model;
  +
  this._refreshLastCaretIfNeeded();
  const selection = document.getSelection();
  if (this._hasTextSelected && selection.isCollapsed) {
  @@ -366,7 +368,7 @@ export default class BasicMessageEditor extends React.Component {
  if (this._formatBarRef) {
  this._formatBarRef.hide();
  }
  - } else if (!selection.isCollapsed) {
  + } else if (!selection.isCollapsed && !isEmpty) {
  this._hasTextSelected = true;
  if (this._formatBarRef) {
  const selectionRect = selection.getRangeAt(0).getBoundingClientRect();
  