message: unbreak modifier+space (e.g. emoji insert on macOS)
diff: @@ -713,6 +713,10 @@ export default class MessageComposerInput extends React.Component {
  };
  onSpace = (ev: KeyboardEvent, change: Change): Change => {
  + if (ev.metaKey || ev.altKey || ev.shiftKey || ev.ctrlKey) {
  + return;
  + }
  +
  // drop a point in history so the user can undo a word
  // XXX: this seems nasty but adding to history manually seems a no-go
  ev.preventDefault();
  