Merge pull request #797 from stozze/2.4-bugfix

BUGFIX Fix to prevent unintended results from getComponentsQuery(...)

core/model/DataObject.php

@@ -1307,7 +1307,7 @@ public function getComponentsQuery($componentName, $filter = "", $sort = "", $jo
 
 		// get filter
 		$combinedFilter = "\"$joinField\" = '$id'";
-		if($filter) $combinedFilter .= " AND {$filter}";
+		if(!empty($filter)) $combinedFilter .= " AND ({$filter})";
 
 		return singleton($componentClass)->extendedSQL($combinedFilter, $sort, $limit, $join);
 	}