fix overview pagination link for 'next window'

If you're on page 5 that shows tickets 101-125 and you click on ">>" you'll get pages 6 to 10 in the pagination navbar and you'll see tickets 125 - 149 (instead of 126 - 150). So page "6" isn't highlighted, too.

With this fix (where the code change is fewer chars than my git branch name ;-) ) the behaviour is correct: you'll see tickets 126 - 150 and page "6" is highlighted.