Fix the panic()s in the v4l2 lib when the device is unplugged

[MartijnBraam]

The current error handling method of gov4l is panic() instead of forwarding the error. Unsure yet how errors should be processed with the goroutine in the lib but I guess another channel with errors?

[dexterlb]

I am planning to ditch that goroutine altogether, and use the frame forwarder. In that case, we should be able to correctly handle errors by calling FailedWriting on the frame forwarder