fix a crash when freeing dynamically loaded sounds

src/include/sound_server.h

@@ -71,6 +71,7 @@ extern bool SampleIsPlaying(Mix_Chunk *sample);
 extern Mix_Music *LoadMusic(const std::string &name);
 /// Load a sample
 extern Mix_Chunk *LoadSample(const std::string &name);
+extern void FreeSample(Mix_Chunk *sample);
 /// Play a sample
 extern int PlaySample(Mix_Chunk *sample, Origin *origin = NULL);
 /// Play a sound file

src/sound/sound.cpp

@@ -411,7 +411,7 @@ static void PlaySoundFileCallback(int channel)
 	}
 	Mix_Chunk *sample = GetChannelSample(channel);
 	if (sample) {
-		Mix_FreeChunk(sample);
+		FreeSample(sample);
 	}
 }
 
@@ -590,13 +590,13 @@ CSound::~CSound()
 {
 	if (this->Number == ONE_SOUND) {
 		if (Sound.OneSound) {
-			Mix_FreeChunk(Sound.OneSound);
+			FreeSample(Sound.OneSound);
 		}
 	} else if (this->Number == TWO_GROUPS) {
 	} else {
 		for (int i = 0; i < this->Number; ++i) {
 			if (this->Sound.OneGroup[i]) {
-				Mix_FreeChunk(this->Sound.OneGroup[i]);
+				FreeSample(this->Sound.OneGroup[i]);
 			}
 			this->Sound.OneGroup[i] = NULL;
 		}

src/sound/sound_server.cpp

@@ -444,6 +444,21 @@ Mix_Chunk *LoadSample(const std::string &name)
 	return sample;
 }
 
+/**
+ * Free a sample loaded with LoadSample.
+ * 
+ * @param sample 
+ */
+void FreeSample(Mix_Chunk *sample)
+{
+#ifdef DYNAMIC_LOAD
+	if (sample->allocated == 0xcafebeef) {
+		return;
+	}
+#endif
+	Mix_FreeChunk(sample);
+}
+
 /**
 **  Play a sound sample
 **