[feladat @ 208] When in the zone listing letters are shown (too many zones to show on a single screen), the start letter is clickable only if there are any zones starting with that letter. If the users asks for a start letter that has no zones (because of bugs like the one fixed in r207 or because user manipulates URL in browser), a PHP error was shown. Code now verifies number of zones now first.

[feladat @ 207] Bugfix. The letters shown just above the list of zones was showing clickable letters, even if there were no zones starting with such a letter.