With beta12, IABot made this edit and this edit.
This seems to have to do with the fact that there is a bare URL in the reference, as can be seen in this test edit.
In general, replacing {{Toter Link}} with {{Webarchiv}} works well. It might be that this bug has been there all along, but it is only now that IABot starts to frequently go over its old edits that this edge case surfaces?
More examples: Diff and diff. They are collected now in Kategorie:Wikipedia:Vorlagenfehler/Parameter:URL, although this is a generic maintenance category which will catch all sorts of other malformatted URLs as well.
I fixed about a hundred occurences after IABot ran for 12 hours and I will continue to do so on a regular basis until this bug has been fixed, as it is the only bug that has surfaced so far and only affects very few articles. If you need more diffs, let me know.