Undefined offset at terms overview if no terms exist

At admin/structure/taxonomy/[name of vocabulary] private_taxonomy_post_render() assumes 1 or more terms will be present in the form. When there are 0 terms $matches is empty, $matches[1] is undefined, and $name becomes FALSE.
The notice is as follow and does not appear immediately after it's generated because it's in a theme function:

Notice: Undefined offset: 1 in private_taxonomy_post_render() (line 573 of private_taxonomy/private_taxonomy.module).