init language object before using it

settings/ajax/removeuser.php

@@ -21,5 +21,6 @@ if( OC_User::deleteUser( $username )) {
 	OC_JSON::success(array("data" => array( "username" => $username )));
 }
 else{
+	$l = OC_L10N::get('core');
 	OC_JSON::error(array("data" => array( "message" => $l->t("Unable to delete user") )));
 }