Display page count if no style is defined.

The page count variable should be shown if there is no  num-style defined.
Use the same way as is used for the page number.

This fixes roundtrip of saving page count variable.

Please review for backporting to 2.4

CCMAIL: calligra-devel@kde.org
BUG: 295604

Reviewed by: boemann
(cherry picked from commit e4f72115)