Ubuntu Bionic, suspicious compiler warning

I have noticed recently this suspicous compiler warning:

2021-01-28T01:06:07.1856464Z /home/runner/work/mixxx/mixxx/src/sources/soundsourceproxy.cpp: In member function ‘void SoundSourceProxy::updateTrackFromSource(SoundSourceProxy::ImportTrackMetadataMode)’:
2021-01-28T01:06:07.1864189Z ##[warning]/home/runner/work/mixxx/mixxx/src/sources/soundsourceproxy.cpp:542:16: warning: ‘*((void*)& preciseStreamInfo +16)’ may be used uninitialized in this function [-Wmaybe-uninitialized]
2021-01-28T01:06:07.1943003Z const auto preciseStreamInfo = trackMetadata.getStreamInfo();
2021-01-28T01:06:07.1945857Z [ 59%] Building CXX object CMakeFiles/mixxx-lib.dir/src/sources/soundsourcesndfile.cpp.o
2021-01-28T01:06:07.1948536Z ^~~~~~~~~~~~~~~~~

I have tried to dig it down but gdb reports that preciseStreamInfo is not an lvalue, which is even more suspicious.

The address +16 points to OptionalSampleLayout.

I think using a optional here is wrong from the business logic anyway, because we can only use the described buffer if we know the sample layout.

I think I will provide a patch that fixes both in one run.