postProcess.H: clear the object owned by the mesh objectRegistry

at the end of each time processed to ensure all fields are updated for each
time.

Resolves bug-report https://bugs.openfoam.org/view.php?id=2997

src/OpenFOAM/db/functionObjects/functionObjectList/postProcess.H

@@ -155,6 +155,9 @@ if (argList::postProcess(argc, argv))
             Warning<< err << endl;
         }
 
+        // Clear the objects owned by the mesh
+        mesh.objectRegistry::clear();
+
         Info<< endl;
     }