--- /public_html/modules/ReferencedByFilter/ReferencedByFilter.old	2008-01-14 06:22:00.000000000 -0500
+++ /public_html/modules/ReferencedByFilter/ReferencedByFilter.module	2008-01-23 21:41:20.000000000 -0500
@@ -123,12 +123,17 @@ function referencedbyfilter_arg_nid($op,
 	        $node = node_load($nid);
 	        $selectStr = ' ';
 
+//patch, check for non-mandatory not existent node references
+			if (array_key_exists($referencing_field, $node)) {
+
 	        foreach ($node->$referencing_field as $referenced) {
 	        	$selectStr .= $referenced['nid']. ',';
 	        }
 	        $query->add_where('node.nid in ('. substr($selectStr,0,-1) . ') ');
-			
-
+			} else {
+// no node-references, select have to give no records
+	        $query->add_where('node.nid <0 ');
+			}
 // this retrieves the nodes that reference $nid
 	        //$query->add_table($node_reference_table, false, 1, array('left' => array('table' => 'node', 'field' => 'nid'), 'right' => array('field' => 'nid')));
 	        //$query->add_where($node_reference_table .'.'. $referencing_field .' = %d', $nid);