message: clean up promises properly
diff: @@ -45,7 +45,7 @@ const singleMxcUpload = async () => {
  Modal.createTrackedDialog('Upload Files confirmation', '', UploadConfirmDialog, {
  file,
  onFinished: (shouldContinue) => {
  - if (shouldContinue) resolve(MatrixClientPeg.get().uploadContent(file));
  + resolve(shouldContinue ? MatrixClientPeg.get().uploadContent(file) : null);
  },
  });
  };
  @@ -246,6 +246,7 @@ export const CommandMap = {
  }
  return success(promise.then((url) => {
  + if (!url) return;
  const ev = room.currentState.getStateEvents('m.room.member', userId);
  const content = {
  ...ev ? ev.getContent() : { membership: 'join' },
  @@ -267,6 +268,7 @@ export const CommandMap = {
  }
  return success(promise.then((url) => {
  + if (!url) return;
  return MatrixClientPeg.get().setAvatarUrl(url);
  }));
  },
  