A patch to fix audio_alsa_sink[hw:0,0]: snd_pcm_hw_params failed

Last night, while I was preparing for the AMSAT-OZ satellite weekend, I noticed that my gqrx receiver didn’t work very well on my laptops. Every time I tried to change operating mode the receiver stopped with a runtime error:

audio_alsa_sink[hw:0,0]: snd_pcm_hw_params failed: File descriptor in bad state
terminate called after throwing an instance of 'std::runtime_error'
what():  check topology failed on audio_alsa_sink(1) using ninputs=1, noutputs=0

This happened on both my Acer and my MacBook Pro; both running the lates git of GNU Radio v3.3.1git-96-g1fa9a8ea. This was bad news because I was hoping to show off my new software receiver with Qt GUI during the weekend. Fortunately, there is an easy workaround that eliminates the problem.

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