Fix panic in fuzzy-finder for unicode characters (#7080)

This fixes a panic in the fuzzy finder which someone ran into when
typing in a query that contained the lower-case version of a unicode
character that has more chars than its upper-case version.

It also fixes another problem which was that we didn't find a match if
both candidates and query contained upper-case characters whose
lower-case version had more chars.


Release Notes:

- Fixed a panic in fuzzy-finder that could occur when matching with
queries containing upper-case unicode characters whose lower-case
version has more chars.

Co-authored-by: bennetbo <bennetbo@gmx.de>