Allow for separate headers upon conditional

html/includes/forms/update-config-item.inc.php

@@ -11,9 +11,9 @@
  * option) any later version.  Please see LICENSE.txt at the top level of
  * the source code distribution for details.
  */
-header('Content-type: application/json');
 
 if (is_admin() === false) {
+	header('Content-type: text/plain');
     die('ERROR: You need to be admin');
 }
 
@@ -100,4 +100,5 @@ $response = array(
     'status'  => $status,
     'message' => $message,
 );
+header('Content-type: application/json');
 echo _json_encode($response);