message: Fix softcrash if editing silly events
  If you sent an event with a body of the empty json object, riot
  would then softcrash when you pressed the up arrow because it
  would try to treat a json object as a string and run split on it.
diff: @@ -52,6 +52,7 @@ export function canEditContent(mxEvent) {
  const content = mxEvent.getOriginalContent();
  const {msgtype} = content;
  return (msgtype === "m.text" || msgtype === "m.emote") &&
  + content.body && typeof content.body === 'string' &&
  mxEvent.getSender() === MatrixClientPeg.get().getUserId();
  }
  