[REVIEW 3-6] Fix for fdo#48868

Hi there,

I'd like

https://gerrit.libreoffice.org/gitweb?p=core.git;a=commitdiff;h=e704e4691186c23e52490817d6b710ef5bf68db6

cherry-picked to 3-6 which fixes

https://bugs.freedesktop.org/show_bug.cgi?id=48868

This is a regression from 3.5.  It's a pretty safe change IMO.

Two things were wrong that contributed to the regression.

1) when cycling through candidate values, the search started with the
previous match, which is always a match (!).  This caused the auto
completion value to never cycle.
2) the current match position was always supposed to point to a valid
candidate value, and never supposed to point to the iterator end
position.

That above commit fixes both, for both column value auto completion
and the formula function in a tool tip.

Review and cherry-pick appreciated.

Kohei