[TF2] Exported Replay files have no audio

[EricZhang456]

Replay movie files rendered in the latest build of TF2 won't have an audio track. If you choose to render TGA/WAV files, the game simply creates a WAV file with no audio in it.

[halamix2]

On Fedora Linux, regular TF2 (not Frog Fortress):

• exporting as .wav/.tga correctly exports .tga files, .wav file is only 44B long
  • it's just the headers (RIFF, WAVE (stereo 44100khz 16bit, dwAvgBytesPerSec 176400), and then one data chunk, with its size set to 0)
  • Team Fortress 2/tf/tmpaudio.wav gets created during export (and deleted afterwards), but it's still only 44B long
    • replacing this file with empty initialized one (st least the length of the clip) does nothing; old workaround on https://wiki.teamfortress.com/wiki/Replay is wrong (or was working for the quicktime renderer)
• exporting to .webm crashes instantly; but that's probably another issue