SCI: Fixed fading-related bugs #3267956 and #3041738

engines/sci/sound/soundcmd.cpp

@@ -325,6 +325,14 @@ reg_t SoundCommandParser::kDoSoundFade(int argc, reg_t *argv, reg_t acc) {
 		return acc;
 	}
 
+	// If the current volume of the slot is the same as the target volume,
+	// return without performing any fading. This fixes the music in room
+	// 406 in KQ6 (bug #3267956), where the game scripts ask for the background
+	// music to be played, and then faded to volume 127 (but the music is
+	// already at volume 127) and subsequently stopped.
+	if (argc >= 4 && musicSlot->volume == CLIP<uint16>(argv[1].toUint16(), 0, MUSIC_VOLUME_MAX))
+		return acc;
+
 	switch (argc) {
 	case 1: // SCI0
 		// SCI0 fades out all the time and when fadeout is done it will also