The sc_uhid_devices instance is initialized only when there is a UHID
keyboard.
The device message receiver assumed that it could not receive HID output
reports without a sc_uhid_devices instance (i.e. without a UHID
keyboard), but in practice, a UHID driver implementation on the device
may decide to send UHID output reports for mouse or for gamepads (and we
must just ignore them).
So remove the assert().
PR #5270 <https://github.com/Genymobile/scrcpy/pull/5270>