#505 Fix small bug in Ensight for Stokes: a singleton was not properly created before use.

Sources/ModelInstances/Stokes/main_ensight_output_monolithic.cpp

@@ -56,7 +56,7 @@ int main(int argc, char ** argv)
             const GeometricMeshRegion& mesh = mesh_manager.GetMesh(EnumUnderlyingType(MeshIndex::mesh));
             
             {
-                auto& manager = Internal::NumberingSubsetNS::NumberingSubsetManager::GetInstance();
+                auto& manager = Internal::NumberingSubsetNS::NumberingSubsetManager::CreateOrGetInstance();
                 Advanced::SetFromInputParameterData<>(input_parameter_data, manager);
             }