MP Core s_sound: I_FadeSongFromVolume call fix (buildbots)

src/s_sound.c

@@ -1716,7 +1716,7 @@ boolean S_FadeMusicFromVolume(UINT8 target_volume, INT16 source_volume, UINT32 m
 	if (source_volume < 0)
 		return I_FadeSong(target_volume, ms, NULL);
 	else
-		return I_FadeSongFromVolume(target_volume, source_volume, ms, false);
+		return I_FadeSongFromVolume(target_volume, source_volume, ms, NULL);
 }
 
 boolean S_FadeOutStopMusic(UINT32 ms)