Fix strict standards error (PHP 5.4+) in resource/getlist processor

The resources grid/list in a collection cannot be displayed in PHP 5.4+ due to a strict standards error (tested in 2.2.x):

<b>Strict Standards</b>:  Declaration of CollectionsResourceGetListProcessor::prepareRow() should be compatible with modObjectGetListProcessor::prepareRow(xPDOObject $object)

with the provided fix the grid loads again.