message: fix: Don't panic in btleplug on disconnect during initialize()
  If a device disconnects while its initialize() is running, don't try
  to send a message to the output_sender (which currently panics).
diff: @@ -347,8 +347,15 @@ impl<T: Peripheral> BtlePlugInternalEventLoop<T> {
  "Device {:?} disconnected",
  self.device.properties().local_name
  );
  - // This should always succeed, as it'll relay up to the device manager,
  - // and that's what owns us.
  +
  + // If output_sender isn't hooked up to anything (for instance, if we
  + // disconnect while initializing), we have no one to relay this info to.
  + // However, that doesn't really matter because we won't have emitted the
  + // device as connected yet.
  + if self.output_sender.receiver_count() == 0 {
  + return true;
  + }
  +
  self
  .output_sender
  .send(ButtplugDeviceEvent::Removed(
  