AOE advanced realurl path

When the query on the lookup table returns no result, a php database warning is thrown.

Sample configuration of a postVarSet:

'product' => array(
    array(
        'GETvar' => 'tx_monierproduct_single[id]',
        'lookUpTable' => array(
            'table' => 'tx_monierproduct_mainproduct',
            'id_field' => 'uid',
            'alias_field' => 'title',
            'addWhereClause' => ' AND NOT deleted AND pid=3171',
            'useUniqueCache' => 1,
            'useUniqueCache_conf' => array(
                'strtolower' => 1,
                'spaceCharacter' => '-',
            ), 
        ), 
    ), 
),

so when there's no matching title on the given pid, the mySQL result is empty and a warnings are thrown.