Fix PolyVox library versioning

There's no need to link PolyVox against 'nothing'

source/Region.cpp

@@ -63,4 +63,4 @@ namespace PolyVox
 		m_v3dUpperCorner.setY((std::min)(m_v3dUpperCorner.y(), other.m_v3dUpperCorner.y()));
 		m_v3dUpperCorner.setZ((std::min)(m_v3dUpperCorner.z(), other.m_v3dUpperCorner.z()));
 	}
-}
+}