Mute sounds with 0 volume when game is minimized/unfocused instead of Stopping all sounds. Fixes (#4336)

code/client/snd_mix.c

@@ -637,7 +637,10 @@ void S_PaintChannels( int endtime ) {
 	int		ltime, count;
 	int		sampleOffset;
 
-	snd_vol = s_volume->value*255;
+	if(s_muted->integer)
+		snd_vol = 0;
+	else
+		snd_vol = s_volume->value*255;
 
 //Com_Printf ("%i to %i\n", s_paintedtime, endtime);
 	while ( s_paintedtime < endtime ) {