Select: Display NULL in column title

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Adminer dev
 - Select: Disable Ctrl+click inline edit without UPDATE privilege
+- Select: Display NULL in column title
 - Export: Remember unchecked objects (regression from 5.0.6)
 - Foreign key: Display new field in case of an error
 - PostgreSQL: Order NULL last

adminer/include/adminer.inc.php

@@ -182,7 +182,7 @@ class Adminer {
 	* @return string HTML code, "" to ignore field
 	*/
 	function fieldName(array $field, int $order = 0): string {
-		$type = $field["full_type"];
+		$type = $field["full_type"] . ($field["null"] ? " NULL" : "");
 		$comment = $field["comment"];
 		return '<span title="' . h($type . ($comment != "" ? ($type ? ": " : "") . $comment : '')) . '">' . h($field["field"]) . '</span>';
 	}