Fixed null values handling for PostgresSQL arrays

Fixes #15804

framework/db/pgsql/ArrayParser.php

@@ -102,6 +102,8 @@ class ArrayParser
 
         if (!$isQuoted && $result === 'NULL') {
             $result = null;
+        } elseif ($isQuoted && $result === '{}') {
+            $result = [];
         }
 
         return $result;