Core/Maps: remove a NULL macro from MapTree

src/common/Collision/Maps/MapTree.cpp

@@ -121,7 +121,7 @@ namespace VMAP
     }
 
     StaticMapTree::StaticMapTree(uint32 mapID, const std::string &basePath)
-        : iMapID(mapID), iTreeValues(NULL), iNTreeValues(0), iBasePath(basePath)
+        : iMapID(mapID), iTreeValues(nullptr), iNTreeValues(0), iBasePath(basePath)
     {
         if (iBasePath.length() > 0 && iBasePath[iBasePath.length()-1] != '/' && iBasePath[iBasePath.length()-1] != '\\')
         {