The module should implement hook_xmlsitemap_links()

The actual code delete the table row referring to the front page all times the sitemap content needs to be updated, and then re-creates it.
It would be better if the code would rather update that row when present, and create a new table row when it's not present.

The code can also be simplified, if the module would implement hook_xmlsitemap_links() as the other modules do.