The API is inconsistent regarding the existence of deleted wikis. Krinkle (bug 27994) and Reedy (bug 28384) suggest the wikis were not removed from all dblists.
For example, the Bashkir Wiktionary is listed by globaluserinfo, but does not exist according to sitematrix. This causes problems for scripts that cross-reference the dbname to the details gathered from the site matrix.
I encountered this problem with the following dbnames: