Call Mix_VolumeMusic() when playing tracks 0 and 7

This fixes issues where they would be silent for 1 frame due to frame
ordering, resulting in a weird-sounding beginning of these tracks due to
a lack of attack (in the musical sense).

This is similar to the issue where tracks fading in would suddenly be
loud for 1 frame, again due to frame ordering.

desktop_version/src/Music.cpp

@@ -213,6 +213,7 @@ void musicclass::play(int t)
 		else
 		{
 			musicVolume = MIX_MAX_VOLUME;
+			Mix_VolumeMusic(musicVolume);
 		}
 	}
 	else