Fix escaping in action error URL (#27273)

This URL is generated on the client (there's an equivalent but shorter
SSR version too) when a function is used as an action. It should never
happen but it'll be invoked if a form is manually submitted or event is
stopped early.

The `'` wasn't escaped so this yielded invalid syntax. Which is an error
too but much less helpful. `missing ) after argument list`. Added a test
that evals to make sure it's correct syntax.