message: Recheck message actions on decrypt
  This changes the message action bar to force an update after an event decrypts,
  since it's quite likely that changes the set of available actions.
  Fixes
diff: @@ -36,6 +36,20 @@ export default class MessageActionBar extends React.PureComponent {
  onFocusChange: PropTypes.func,
  };
  + componentDidMount() {
  + this.props.mxEvent.on("Event.decrypted", this.onDecrypted);
  + }
  +
  + componentWillUnmount() {
  + this.props.mxEvent.removeListener("Event.decrypted", this.onDecrypted);
  + }
  +
  + onDecrypted = () => {
  + // When an event decrypts, it is likely to change the set of available
  + // actions, so we force an update to check again.
  + this.forceUpdate();
  + }
  +
  onFocusChange = (focused) => {
  if (!this.props.onFocusChange) {
  return;
  