can't open hackrf_sink with device index
When using a hackrf_source with gr-osmosdr, I can select the device by its index (usually 0) instead of the serial number.
Opening a hackrf_sink this way fails. ("RuntimeError: Failed to open HackRF device (-5) HackRF not found")
Using hackrf_sink only works when supplying the full serial number.
There is a check in hackrf_source_c.cc#n152 that detects when a device is selected by index instead of the serial number.
This check is missing in hackrf_sink_c.cc.