Infinite redirect when user is disabled

[nickvergessen]

Steps to reproduce

1. Have a saml user that is disabled
2. Try to authenticate as that user

Expected behaviour

Error message is displayed

Actual behaviour

user_saml/appinfo/app.php

Lines 110 to 120 in a7aabdd

	$enabled = $user->isEnabled();
	if ($enabled === false) {
	$targetUrl = $urlGenerator->linkToRouteAbsolute(
	'user_saml.SAML.genericError',
	[
	'message' => $l->t('This user account is disabled, please contact your administrator.')
	]
	);
	header('Location: '.$targetUrl);
	exit();
	}

1. This code path will redirect to an error page.
2. When the error page is being accessed, see step 1.

Server configuration

Master of all repos