Fixed a shutdown crash in LLAudioEngine::assetCallback, and fixed behavior when soundsource re-issues a sound whilst a sound is currently playing for same source. (LLAudioChannel[Impl]::play now re-starts sound if already playing)

indra/llaudio/llaudioengine.cpp

@@ -1249,6 +1249,9 @@ void LLAudioEngine::startNextTransfer()
 // static
 void LLAudioEngine::assetCallback(LLVFS *vfs, const LLUUID &uuid, LLAssetType::EType type, void *user_data, S32 result_code, LLExtStat ext_status)
 {
+	if(!gAudiop)
+		return;
+
 	if (result_code)
 	{
 		LL_INFOS("AudioEngine") << "Boom, error in audio file transfer: " << LLAssetStorage::getErrorString( result_code ) << " (" << result_code << ")" << LL_ENDL;
@@ -1469,6 +1472,19 @@ bool LLAudioSource::play(const LLUUID &audio_uuid)
 			return true;
 		}
 	}
+	else if(mCurrentDatap == adp)	//Desired sound did not change. Just re-play it.
+	{
+		if(getChannel() && getChannel()->isPlaying())
+			getChannel()->play();
+		return true;
+	}
+	else							//Desired sound did change. Release the old channel if set.
+	{
+		if(getChannel())
+			getChannel()->cleanup();
+		mPlayedOnce = false;		//Reset the played flag so the new sound is actually started up.
+	}
+
 	mCurrentDatap = adp;
 
 	// Make sure the audio engine knows that we want to request this sound.