[feladat @ 87] Bugfix. With user level 5 or 10 and lots of zones without an owner, like slave zones that are inserted by a supermaster, the "list all zones" view was broken (not all zones shown, but "show page" and "show letters" were missing as well). Function zone_count matches zones and domains table, but users with level 5 or 10 are allowed to see zones without an entry in the zones table as well.