In 1f8013ff3f, I mistakenly thought this
was only used for modifier presses way back in the commit it was
introduced in, but it actually also handles non-english keys/letters.
Instead of returning early, we should try xkb_keysym_to_utf8 first and
then return if that doesn't do anything so the modifier can then be
handled in the appropriate event. Fixes#12009.