adjust use of qs-invalid-hook so that it gets used at runtime

[rfindler]

The string-constants syntactic form is meant to be used only at runtime, not during any higher phases (as the choice of language won't be resolved when compiling the source code).

This pull request is one way to bring back the use of qs-invalid-hook. I'm not sure if it a good way to go. It might be better to just not translation this part, maybe.

I also did not test out how this works so that should be done before we merge.

[Metaxal]

Seems fine to me. A test case would be nice for sure :) Feel free to merge when you are satisfied.