fixed a minor regression in PSSMLT

src/integrators/pssmlt/pssmlt.cpp

@@ -321,7 +321,7 @@ public:
 
 		if (m_config.workUnits <= 0) 
 			m_config.workUnits = std::max((int) std::ceil((cropSize.x 
-				* cropSize.y * sampleCount) / 200000.0f), 1);
+				* cropSize.y * sampleCount) / (Float) desiredMutationsPerWorkUnit), 1);
 
 		m_config.nMutations = (cropSize.x * cropSize.y *
 			sampleCount) / m_config.workUnits;