fix crash caused by adding DSP_ClearAudioBuffer()

git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@4509 8ced0084-cf51-0410-be5f-012b33b47a6e

Source/Plugins/Plugin_DSP_HLE/Src/main.cpp

@@ -385,5 +385,6 @@ void DSP_SendAIBuffer(unsigned int address, int sample_rate)
 
 void DSP_ClearAudioBuffer()
 {
-	soundStream->Clear();
+	if (soundStream)
+		soundStream->Clear();
 }