Crash when file input is used but no file name given

[reald]

Steps to reproduce:

1. Open gqrx and configure i/o device as "Complex Sampled IQ File".
2. Leave defaults (file=/path/to/your/file), select ok
3. gqrx complains that the file cannot be opened. Ignore and hit ok.
4. Go to I/Q recording and replay tool
5. Play a fancy sigmf file
6. After file is completely played hit Play button to end the I/Q recording tool
7. gqrx crashes because it cannot open /path/to/your/file

Affected version: 2.17.5

[vladisslav2011]

Thanks.
Confirmed.
My fork is affected too.
Putting https://github.com/gqrx-sdr/gqrx/blob/master/src/applications/gqrx/mainwindow.cpp#L1766 into try...catch block fixes the issue.
Possible fix: vladisslav2011@786f00f