output/Source: convert prepared_filter to reference

src/output/Source.cxx

@@ -33,7 +33,7 @@ AudioFormat
 AudioOutputSource::Open(const AudioFormat audio_format, const MusicPipe &_pipe,
 			PreparedFilter *prepared_replay_gain_filter,
 			PreparedFilter *prepared_other_replay_gain_filter,
-			PreparedFilter *prepared_filter)
+			PreparedFilter &prepared_filter)
 {
 	assert(audio_format.IsValid());
 
@@ -90,7 +90,7 @@ void
 AudioOutputSource::OpenFilter(AudioFormat audio_format,
 			      PreparedFilter *prepared_replay_gain_filter,
 			      PreparedFilter *prepared_other_replay_gain_filter,
-			      PreparedFilter *prepared_filter)
+			      PreparedFilter &prepared_filter)
 try {
 	assert(audio_format.IsValid());
 
@@ -107,7 +107,7 @@ try {
 			prepared_other_replay_gain_filter->Open(audio_format);
 	}
 
-	filter_instance = prepared_filter->Open(audio_format);
+	filter_instance = prepared_filter.Open(audio_format);
 } catch (...) {
 	CloseFilter();
 	throw;

src/output/Source.hxx

@@ -136,7 +136,7 @@ public:
 	AudioFormat Open(AudioFormat audio_format, const MusicPipe &_pipe,
 			 PreparedFilter *prepared_replay_gain_filter,
 			 PreparedFilter *prepared_other_replay_gain_filter,
-			 PreparedFilter *prepared_filter);
+			 PreparedFilter &prepared_filter);
 
 	void Close() noexcept;
 	void Cancel() noexcept;
@@ -195,7 +195,7 @@ private:
 	void OpenFilter(AudioFormat audio_format,
 			PreparedFilter *prepared_replay_gain_filter,
 			PreparedFilter *prepared_other_replay_gain_filter,
-			PreparedFilter *prepared_filter);
+			PreparedFilter &prepared_filter);
 
 	void CloseFilter() noexcept;
 

src/output/Thread.cxx

@@ -148,7 +148,7 @@ AudioOutputControl::InternalOpen(const AudioFormat in_audio_format,
 			f = source.Open(in_audio_format, pipe,
 					output->prepared_replay_gain_filter,
 					output->prepared_other_replay_gain_filter,
-					output->prepared_filter);
+					*output->prepared_filter);
 		} catch (...) {
 			std::throw_with_nested(FormatRuntimeError("Failed to open filter for %s",
 								  GetLogName()));