Make audio asset decoding failures non-fatal

Matches RMXP behavior. This is also useful in case midi files
are to be played, but fluidsynth isn't available.

src/alstream.cpp

@@ -25,9 +25,11 @@
 #include "sharedmidistate.h"
 #include "eventthread.h"
 #include "filesystem.h"
+#include "exception.h"
 #include "aldatasource.h"
 #include "fluid-fun.h"
 #include "sdl-util.h"
+#include "debugwriter.h"
 
 #include <SDL_mutex.h>
 #include <SDL_thread.h>
@@ -123,6 +125,9 @@ void ALStream::stop()
 
 void ALStream::play(float offset)
 {
+	if (!source)
+		return;
+
 	checkStopped();
 
 	switch (state)
@@ -205,6 +210,8 @@ void ALStream::openSource(const std::string &filename)
 	SDL_RWread(&srcOps, sig, 1, 4);
 	SDL_RWseek(&srcOps, 0, RW_SEEK_SET);
 
+	try
+	{
 		if (!strcmp(sig, "OggS"))
 		{
 			source = createVorbisSource(srcOps, looped);
@@ -223,6 +230,16 @@ void ALStream::openSource(const std::string &filename)
 		}
 
 		source = createSDLSource(srcOps, ext, STREAM_BUF_SIZE, looped);
+	}
+	catch (const Exception &e)
+	{
+		char buf[512];
+		snprintf(buf, sizeof(buf), "Unable to decode audio stream: %s.%s: %s",
+		         filename.c_str(), ext, e.msg.c_str());
+		buf[sizeof(buf)-1] = '\0';
+
+		Debug() << buf;
+	}
 }
 
 void ALStream::stopStream()

src/soundemitter.cpp

@@ -26,6 +26,7 @@
 #include "exception.h"
 #include "config.h"
 #include "util.h"
+#include "debugwriter.h"
 
 #include <SDL_sound.h>
 
@@ -127,6 +128,9 @@ void SoundEmitter::play(const std::string &filename,
 
 	SoundBuffer *buffer = allocateBuffer(filename);
 
+	if (!buffer)
+		return;
+
 	/* Try to find first free source */
 	size_t i;
 	for (i = 0; i < srcCount; ++i)
@@ -206,9 +210,13 @@ SoundBuffer *SoundEmitter::allocateBuffer(const std::string &filename)
 
 		if (!sampleHandle)
 		{
-			SDL_RWclose(&dataSource);
-			throw Exception(Exception::SDLError, "%s.%s: %s",
-			                filename.c_str(), extension, Sound_GetError());
+			char buf[512];
+			snprintf(buf, sizeof(buf), "Unable to decode sound: %s.%s: %s",
+			         filename.c_str(), ext, Sound_GetError());
+			buf[sizeof(buf)-1] = '\0';
+			Debug() << buf;
+
+			return 0;
 		}
 
 		uint32_t decBytes = Sound_DecodeAll(sampleHandle);