Fixing read of atomic pointer in assertion call

src/Rendering/Ambient/Mixer/VAAmbientMixerAudioRenderer.cpp

@@ -140,7 +140,7 @@ void CVAAmbientMixerAudioRenderer::HandleProcessStream( ITADatasourceRealization
 
 			const double dGainFactor = pState->GetVolume( m_oParams.pCore->GetCoreConfig()->dDefaultAmplitudeCalibration );
 
-			assert( pDesc->pSignalSource );
+			assert( pDesc->pSignalSource.load() );
 			const ITASampleBuffer* psbInput = pDesc->pSignalSourceInputBuf;
 
 			// Add samples to out buffer