Fix crash when passing null to AudioStreamPlayer::set_stream()

scene/2d/audio_stream_player_2d.cpp

@@ -272,7 +272,10 @@ void AudioStreamPlayer2D::_notification(int p_what) {
 
 void AudioStreamPlayer2D::set_stream(Ref<AudioStream> p_stream) {
 	// Instancing audio streams can cause large memory allocations, do it prior to AudioServer::lock.
-	Ref<AudioStreamPlayback> pre_instanced_playback = p_stream->instance_playback();
+	Ref<AudioStreamPlayback> pre_instanced_playback;
+	if (p_stream.is_valid()) {
+		pre_instanced_playback = p_stream->instance_playback();
+	}
 
 	AudioServer::get_singleton()->lock();
 

scene/3d/audio_stream_player_3d.cpp

@@ -623,7 +623,10 @@ void AudioStreamPlayer3D::_notification(int p_what) {
 
 void AudioStreamPlayer3D::set_stream(Ref<AudioStream> p_stream) {
 	// Instancing audio streams can cause large memory allocations, do it prior to AudioServer::lock.
-	Ref<AudioStreamPlayback> pre_instanced_playback = p_stream->instance_playback();
+	Ref<AudioStreamPlayback> pre_instanced_playback;
+	if (p_stream.is_valid()) {
+		pre_instanced_playback = p_stream->instance_playback();
+	}
 
 	AudioServer::get_singleton()->lock();
 

scene/audio/audio_stream_player.cpp

@@ -168,7 +168,10 @@ void AudioStreamPlayer::_notification(int p_what) {
 
 void AudioStreamPlayer::set_stream(Ref<AudioStream> p_stream) {
 	// Instancing audio streams can cause large memory allocations, do it prior to AudioServer::lock.
-	Ref<AudioStreamPlayback> pre_instanced_playback = p_stream->instance_playback();
+	Ref<AudioStreamPlayback> pre_instanced_playback;
+	if (p_stream.is_valid()) {
+		pre_instanced_playback = p_stream->instance_playback();
+	}
 
 	AudioServer::get_singleton()->lock();