ENH: add PDRblock::null() member - reference to NullObject

src/mesh/blockMesh/PDRblockMesh/PDRblock.C

@@ -72,6 +72,12 @@ bool Foam::PDRblock::checkMonotonic
 }
 
 
+const Foam::PDRblock& Foam::PDRblock::null()
+{
+    return NullObjectRef<PDRblock>();
+}
+
+
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
 void Foam::PDRblock::adjustSizes()

src/mesh/blockMesh/PDRblockMesh/PDRblock.H

@@ -94,10 +94,12 @@ public:
         //- Grid locations in an axis direction.
         //  The number of points is one larger than the number of elements
         //  it represents
-        struct location
+        class location
         :
             public scalarList
         {
+        public:
+
             //- The locations are valid if they contain 2 or more points
             inline bool valid() const;
 
@@ -187,7 +189,11 @@ private:
     // Private Member Functions
 
         //- Check that points increase monotonically
-        static bool checkMonotonic(const direction cmpt, const UList<scalar>& pts);
+        static bool checkMonotonic
+        (
+            const direction cmpt,
+            const UList<scalar>& pts
+        );
 
         //- Adjust sizing for updated grid points
         void adjustSizes();
@@ -242,6 +248,12 @@ private:
 
 public:
 
+    // Static Member Functions
+
+        //- Return a PDRblock reference to a nullObject
+        static const PDRblock& null();
+
+
     // Constructors
 
         //- Construct zero-size