Incorrect check for polyMesh::dbDir()
It checks objectRegistry::dbDir() == defaultRegion
but this only works on the assumption that the polyMesh is rooted directly on time.
If we relocate to a different database (eg, "finite-volume"), the dbDir() would then be something like "finite-volume/region0".
Should be checking on objectRegistry::name() directly, as per polyMesh::regionName().