Adding {invitation_url} to any abstract notification that's not for the "invited" state, it first of all makes no sense (since there is no invitation uuid), but it will also break during abstract submission since it cannot build that URL.

I think the most likely way of this to happen if someone doing basically this:

So adding validation that prevents you from using the "Invited" when any rule but "Invited" is used would already do a lot.

In fact, there should probably be validation that prevents mixing the "invited" rule with any other rule, since it never makes sense to mix those. Also validate it when editing an existing template.