refactor(Core): replace NULL with nullptr (#4593)

src/common/Collision/Management/VMapFactory.cpp

@@ -9,7 +9,7 @@
 
 namespace VMAP
 {
-    IVMapManager* gVMapManager = NULL;
+    IVMapManager* gVMapManager = nullptr;
 
     //===============================================
     // just return the instance
@@ -25,6 +25,6 @@ namespace VMAP
     void VMapFactory::clear()
     {
         delete gVMapManager;
-        gVMapManager = NULL;
+        gVMapManager = nullptr;
     }
 }