Fix the "Illegal string offset" problem when performing a "With Query" with wrong param format.
Turns out, isset has problem to check a string with multi-dimensional indexer. Following code will tell:

<?php

$string = 'this is a string';

if (isset($string['check'][0])) {
    echo 'found';
} else {
    echo 'not found';
}

// Shows found, which should not.