[Audio] Prevent crash in interactive playback

modules/interactive_music/audio_stream_interactive.cpp

@@ -976,6 +976,8 @@ void AudioStreamPlaybackInteractive::switch_to_clip_by_name(const StringName &p_
 		return;
 	}
 
+	ERR_FAIL_COND_MSG(stream.is_null(), "Attempted to switch while not playing back any stream.");
+
 	for (int i = 0; i < stream->get_clip_count(); i++) {
 		if (stream->get_clip_name(i) == p_name) {
 			switch_request = i;

modules/interactive_music/register_types.cpp

@@ -42,11 +42,11 @@
 void initialize_interactive_music_module(ModuleInitializationLevel p_level) {
 	if (p_level == MODULE_INITIALIZATION_LEVEL_SCENE) {
 		GDREGISTER_CLASS(AudioStreamPlaylist);
-		GDREGISTER_VIRTUAL_CLASS(AudioStreamPlaybackPlaylist);
+		GDREGISTER_ABSTRACT_CLASS(AudioStreamPlaybackPlaylist);
 		GDREGISTER_CLASS(AudioStreamInteractive);
-		GDREGISTER_VIRTUAL_CLASS(AudioStreamPlaybackInteractive);
+		GDREGISTER_ABSTRACT_CLASS(AudioStreamPlaybackInteractive);
 		GDREGISTER_CLASS(AudioStreamSynchronized);
-		GDREGISTER_VIRTUAL_CLASS(AudioStreamPlaybackSynchronized);
+		GDREGISTER_ABSTRACT_CLASS(AudioStreamPlaybackSynchronized);
 	}
 #ifdef TOOLS_ENABLED
 	if (p_level == MODULE_INITIALIZATION_LEVEL_EDITOR) {