[ChangeItem] - the check query should return array instead of object - PHP 7.2 (joomla#18443)

* [ChangeItem] - the check query shuold return array instead of object

* add unique

Author: alikon

libraries/src/Schema/ChangeItem.php

@@ -196,7 +196,7 @@ public function check()
 
 			try
 			{
-				$rows = $this->db->loadObject();
+				$rows = $this->db->loadRowList(0);
 			}
 			catch (\RuntimeException $e)
 			{