fix sso redirect when redirectUrl is null

Signed-off-by: Julien Veyssier <julien-nc@posteo.net>

Author: julien-nc

lib/AppInfo/Application.php

@@ -106,7 +106,10 @@ private function registerRedirect(IRequest $request, IURLGenerator $urlGenerator
 			// if the login page's redirect_url GET param is the logout page, just use the base URL instead
 			$logoutUrl = $urlGenerator->linkToRoute('core.login.logout');
 			$userOidcLogoutUrl = $urlGenerator->linkToRoute(self::APP_ID . '.login.singleLogoutService');
-			if (strpos($redirectUrl, $logoutUrl) !== false || strpos($redirectUrl, $userOidcLogoutUrl) !== false) {
+			if (
+				$redirectUrl
+				&& (strpos($redirectUrl, $logoutUrl) !== false || strpos($redirectUrl, $userOidcLogoutUrl) !== false)
+			) {
 				$redirectUrl = $urlGenerator->getBaseUrl();
 			}
 			$targetUrl = $urlGenerator->linkToRoute(self::APP_ID . '.login.login', [