[NL/DOF] Init MeshComponentMap::nop in the class declaration

NumLib/DOF/MeshComponentMap.cpp

@@ -24,9 +24,6 @@ namespace NumLib
 {
 using namespace detail;
 
-GlobalIndexType const MeshComponentMap::nop =
-    std::numeric_limits<GlobalIndexType>::max();
-
 #ifdef USE_PETSC
 MeshComponentMap::MeshComponentMap(
     std::vector<MeshLib::MeshSubset> const& components, ComponentOrder order)

NumLib/DOF/MeshComponentMap.h

@@ -137,7 +137,8 @@ public:
 
     /// A value returned if no global index was found for the requested
     /// location/component. The value is implementation dependent.
-    static NUMLIB_EXPORT GlobalIndexType const nop;
+    static constexpr NUMLIB_EXPORT GlobalIndexType const nop =
+        std::numeric_limits<GlobalIndexType>::max();
 
 #ifndef NDEBUG
     const detail::ComponentGlobalIndexDict& getDictionary() const