This is an issue on the newest PHP version, and will be fixed in the upcoming Q2A 1.8.
In the meantime you can fix it by changing that line (format.php line 1105) to this:
$lastpage = ceil(min((int)$count, 1 + QA_MAX_LIMIT_START) / $pagesize);
In other words, add (int) before the $count variable.
