Fix error prompt when aborting choosing ref audio

Author: OctoFlareDev

scripts/load_reference_audio/load_reference_audio.gml

@@ -1,4 +1,6 @@
 function load_reference_audio(){
+	var fn = string(get_open_filename_ext("Supported sounds (*.ogg;*.wav)|*.ogg;*.wav", "", songfolder, condstr(language != 1, "Load reference audio", "打开参考音频")))
+	if (fn = "" || !file_exists_lib(fn)) return 0
 	audio_destroy_stream(songs[song].reference_audio)
 	audio_free_buffer_sound(songs[song].reference_audio)
 	buffer_delete(songs[song].reference_audio_buffer)
@@ -10,7 +12,7 @@ function load_reference_audio(){
 	songs[song].reference_offset = 0
 	songs[song].reference_sound = -1
 	songs[song].reference_volume = 100
-	songs[song].reference_audio_file = string(get_open_filename_ext("Supported sounds (*.ogg;*.wav)|*.ogg;*.wav", "", songfolder, condstr(language != 1, "Load reference audio", "打开参考音频")))
+	songs[song].reference_audio_file = fn
 	songs[song].reference_audio = -1
 	if (string_lower(filename_ext(songs[song].reference_audio_file)) == ".ogg") {
 		songs[song].reference_audio = audio_create_stream(songs[song].reference_audio_file)