fix: prevent backup file being saved with .zip extension for packed song

Author: Bentroen

scripts/backup_clear/backup_clear.gml

@@ -34,6 +34,6 @@ function update_backup_name() {
 	// Rename backup file to the current filename. Call when the active file of this window changes.
 
 	file_rename_lib(backup_directory + song_backupname, backup_directory + filename_name(filename))
-	song_backupname = filename_name(filename)
+	song_backupname = filename_name(filename_change_ext(filename, ".nbs"));
 	tonextbackup = backupmins
 }

scripts/control_create/control_create.gml

@@ -692,7 +692,7 @@ function control_create() {
 			// File drop, etc.
 			} else if (string_replace(arg, " ", "") != "") {
 				filename = arg;
-				song_backupname = filename_name(filename);
+				song_backupname = filename_name(filename_change_ext(filename, ".nbs"));
 			}
 
 		}

scripts/control_draw/control_draw.gml

@@ -107,7 +107,7 @@ function control_draw() {
 		tonextbackup -= 1 / room_speed / 60 * (1 / currspeed)
 		if (tonextbackup <= 0 && playing == 0) {
 			if (filename_name(filename) != "") {
-				song_backupname = filename_name(filename)
+				song_backupname = filename_name(filename_change_ext(filename, ".nbs"));
 			} else {
 				song_backupname = "Unsaved song " + string(song_backupid) + ".nbs"
 			}

scripts/load_song/load_song.gml

@@ -46,7 +46,7 @@ function load_song() {
 		add_to_recent(fn)
 		if (window != w_instruments && song_name != "") window = w_songinfo
 		filename = fn
-		song_backupname = filename_name(filename);
+		song_backupname = filename_name(filename_change_ext(filename, ".nbs"));
 		changed = 0
 	}
 	else {