String freeze break for Konversation

Hi,

I've broken the string freeze for a crash fix. The scenario is extremely
uncommon so its unlikely that anyone will ever see it, but the lack of
something to display is the cause of the crash.

If there are any objections I can revert and put in an non-textual
placeholder, but an untranslated string is better than a crash.

The offending commit is
https://invent.kde.org/network/konversation/-/commit/58de7eb18 in the
release/25.12 branch.

Regards, Eli