check ins nums before write

Author: OctoFlareDev

scripts/save_song/save_song.gml

@@ -78,6 +78,12 @@ function save_song() {
 	buffer_write_byte(cursong.loopmax)
 	buffer_write_short(cursong.loopstart)
 	}
+	
+	if (nbsver < 6) {
+		for (var ind = 16; ind < 20; ind++) {
+			if(songs[song].instrument_list[| ind].num_blocks > 0) has_v6_ins = true
+		}
+	}
 
 	ca = 0
 	var ins = 0
@@ -93,7 +99,6 @@ function save_song() {
 	                buffer_write_short(cb)
 	                cb = 0
 					ins = ds_list_find_index(cursong.instrument_list, cursong.song_ins[a, b])
-					if (nbsver < 6 && ins > 15 && ins < 20) has_v6_ins = true
 					if (nbsver < 6 && ins >= 20 && !has_v6_ins) ins -= 4
 	                buffer_write_byte(ins)
 	                buffer_write_byte(cursong.song_key[a, b])