don't freeze game if it fails to find target song/difficulty

Author: VioletSnowLeopard

source/funkin/ui/freeplay/FreeplayState.hx

@@ -2466,6 +2466,8 @@ class FreeplayState extends MusicBeatSubState
     if (targetSongNullable == null)
     {
       FlxG.log.warn('WARN: could not find song with id (${targetSongId})');
+      busy = false;
+      letterSort.inputEnabled = true;
       return;
     }
     var targetSong:Song = targetSongNullable;
@@ -2476,6 +2478,8 @@ class FreeplayState extends MusicBeatSubState
     if (targetDifficulty == null)
     {
       FlxG.log.warn('WARN: could not find difficulty with id (${targetDifficultyId})');
+      busy = false;
+      letterSort.inputEnabled = true;
       return;
     }