WavWriter::finalize didn't check that m_file was actually valid before
trying to seek and close it. The file is only set by set_file, so it's
not an invariant. Just add a null guard to finalize().
This class mirrors WavLoader and uses the same variable names so they
can be read side-by-side.
In a simple use-case, you construct a WavWriter object with your file
path and audio parameters, call write_samples() with your bytes and then
either finalize() to finish writing the file or allow the destructor to
do it automatically.
finalize() is needed because the WAV header cannot be written until the
size of the data section is known. You only need to call this manually
if you want to write a WAV file and then immediately load it.
You can also use one WavWriter instance multiple times by repeatedly
calling finalize() and set_file().