message: Fix a recent regression where uploads would hang.
diff: @@ -983,7 +983,7 @@ function setupPtyManager(): boolean {
  ptyManager.onPtyAvailableWriteBufferSizeChange(event => {
  const senderId = ptyToSenderMap.get(event.ptyId);
  const sender = webContents.fromId(senderId);
  - if (sender == null && ! sender.isDestroyed()) {
  + if (sender != null && ! sender.isDestroyed()) {
  const msg: Messages.PtyInputBufferSizeChange = {
  type: Messages.MessageType.PTY_INPUT_BUFFER_SIZE_CHANGE,
  id: event.ptyId,
  