On line 84, that should look like this:
$WADbSearch1->whereClause .= "ProductID IN (SELECT ProductID FROM ps3_productcategories WHERE (CategoryID = ".implode($_GET["ProductCategoryID"]," OR CategoryID = ")."))";
Change it to look like this:
$WADbSearch1->whereClause .= " ProductID IN (SELECT ProductID FROM ps3_productcategories WHERE (CategoryID = ".implode($_GET["ProductCategoryID"]," OR CategoryID = ").")) ";