Move back to using paComplete

Made a misunderstanding. Pa_StopStream requires that we return paComplete when we are done to tell it that no more new buffers are being rendered for now and it can play any pending audio buffers.

src/core/audio/AudioPortAudio.cpp

@@ -178,7 +178,7 @@ int AudioPortAudio::processCallback(const float* inputBuffer, float* outputBuffe
 			if( !frames )
 			{
 				memset(outputBuffer, 0, framesPerBuffer * channels() * sizeof(float));
-				return paContinue;
+				return paComplete;
 			}
 			m_outBufSize = frames;
 		}