ada_server: fix crash when no devices found
ada_server: fix crash when no devices found

The select of all devices seems to corrupt the initialized std::vector
when count == 0. Do not perform the second select to avoid this crash.

Fixes: 41dadcb31b5b ("commit ada_server")

Acked-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server