PostgreSQL: Fix setting NULL and original value on enum (bug #884)

adminer/drivers/mysql.inc.php

@@ -1159,7 +1159,7 @@ if (!defined('Adminer\DRIVER')) {
 
 	/** Convert value in edit after applying functions back
 	* @param array one element from fields()
-	* @param string
+	* @param string SQL expression
 	* @return string
 	*/
 	function unconvert_field($field, $return) {

adminer/drivers/pgsql.inc.php

@@ -234,6 +234,11 @@ if (isset($_GET["pgsql"])) {
 			}
 		}
 
+		function enumLength($field) {
+			$enum = $this->types[lang('User types')][$field["type"]];
+			return ($enum ? type_values($enum) : "");
+		}
+
 		function setUserTypes($types) {
 			$this->types[lang('User types')] = array_flip($types);
 		}