Music volume not set correctly at startup

[bradharding]

Regardless of what music_volume is set to in doomretro.cfg, music will be played at full volume at startup (the default of 15), unless the player then proceeds to adjust the music volume in the options menu.
The value of music_volume is being set and saved correctly. It doesn't occur to the sfx volume. Checking previous versions of DOOM RETRO, this issue has been present since v1.0. The issue does not occur in the latest release of Chocolate DOOM. It would seem that the initial call to SDL's Mix_VolumeMusic() does nothing, but successive calls to the same function later work fine.
Thanks to @jeffdoggett for picking up on this one. I was hoping a fix could have made it into v1.5, but I have no idea what's causing it. What I may try doing is completely revamping the sound code to match the latest Chocolate DOOM build, since the code I'm using is still based on Chocolate DOOM v1.7.

[bradharding]

Finally fixed due to changes in commits 840160e and f3653a7.