message: dont allow sending empty messages
diff: @@ -203,6 +203,9 @@ export default class SendMessageComposer extends React.Component {
  }
  _sendMessage() {
  + if (this.model.isEmpty) {
  + return;
  + }
  if (!containsEmote(this.model) && this._isSlashCommand()) {
  this._runSlashCommand();
  } else {
  