diff --git a/apps/files_external/lib/Service/UserGlobalStoragesService.php b/apps/files_external/lib/Service/UserGlobalStoragesService.php
index b8ea137428..fc284f951b 100644
--- a/apps/files_external/lib/Service/UserGlobalStoragesService.php
+++ b/apps/files_external/lib/Service/UserGlobalStoragesService.php
@@ -76,7 +76,7 @@ class UserGlobalStoragesService extends GlobalStoragesService {
 		$userMounts = $this->dbConfig->getAdminMountsFor(DBConfigService::APPLICABLE_TYPE_USER, $this->getUser()->getUID());
 		$globalMounts = $this->dbConfig->getAdminMountsFor(DBConfigService::APPLICABLE_TYPE_GLOBAL, null);
 		$groups = $this->groupManager->getUserGroupIds($this->getUser());
-		if (is_array($groups) && count($groups) !== 0) {
+		if (count($groups) !== 0) {
 			$groupMounts = $this->dbConfig->getAdminMountsForMultiple(DBConfigService::APPLICABLE_TYPE_GROUP, $groups);
 		} else {
 			$groupMounts = [];
diff --git a/lib/private/AppFramework/DependencyInjection/DIContainer.php b/lib/private/AppFramework/DependencyInjection/DIContainer.php
index 3ef816f503..7395be703d 100644
--- a/lib/private/AppFramework/DependencyInjection/DIContainer.php
+++ b/lib/private/AppFramework/DependencyInjection/DIContainer.php
@@ -234,6 +234,8 @@ class DIContainer extends SimpleContainer implements IAppContainer {
 				)
 			);
 
+
+
 			$securityMiddleware = new SecurityMiddleware(
 				$c->get(IRequest::class),
 				$c->get(IControllerMethodReflector::class),
@@ -242,7 +244,7 @@ class DIContainer extends SimpleContainer implements IAppContainer {
 				$server->query(ILogger::class),
 				$c->get('AppName'),
 				$server->getUserSession()->isLoggedIn(),
-				$server->getGroupManager()->isAdmin($this->getUserId()),
+				$this->getUserId() !== null && $server->getGroupManager()->isAdmin($this->getUserId()),
 				$server->getUserSession()->getUser() !== null && $server->query(ISubAdmin::class)->isSubAdmin($server->getUserSession()->getUser()),
 				$server->getAppManager(),
 				$server->getL10N('lib')
diff --git a/lib/private/Group/Manager.php b/lib/private/Group/Manager.php
index 4c731a9f48..145b363120 100644
--- a/lib/private/Group/Manager.php
+++ b/lib/private/Group/Manager.php
@@ -276,7 +276,7 @@ class Manager extends PublicEmitter implements IGroupManager {
 	 * @param string $uid the user id
 	 * @return \OC\Group\Group[]
 	 */
-	public function getUserIdGroups($uid) {
+	public function getUserIdGroups(string $uid): array {
 		$groups = [];
 
 		foreach ($this->getUserIdGroupIds($uid) as $groupId) {
@@ -321,17 +321,17 @@ class Manager extends PublicEmitter implements IGroupManager {
 	 * get a list of group ids for a user
 	 *
 	 * @param IUser $user
-	 * @return array with group ids
+	 * @return string[] with group ids
 	 */
-	public function getUserGroupIds(IUser $user) {
+	public function getUserGroupIds(IUser $user): array {
 		return $this->getUserIdGroupIds($user->getUID());
 	}
 
 	/**
 	 * @param string $uid the user id
-	 * @return GroupInterface[]
+	 * @return string[]
 	 */
-	private function getUserIdGroupIds($uid) {
+	private function getUserIdGroupIds(string $uid): array {
 		if (!isset($this->cachedUserGroups[$uid])) {
 			$groups = [];
 			foreach ($this->backends as $backend) {
diff --git a/lib/private/Template/JSConfigHelper.php b/lib/private/Template/JSConfigHelper.php
index b228cae6ff..cd46657560 100644
--- a/lib/private/Template/JSConfigHelper.php
+++ b/lib/private/Template/JSConfigHelper.php
@@ -167,7 +167,7 @@ class JSConfigHelper {
 
 		$countOfDataLocation = 0;
 		$dataLocation = str_replace(\OC::$SERVERROOT . '/', '', $this->config->getSystemValue('datadirectory', ''), $countOfDataLocation);
-		if ($countOfDataLocation !== 1 || !$this->groupManager->isAdmin($uid)) {
+		if ($countOfDataLocation !== 1 || $uid === null || !$this->groupManager->isAdmin($uid)) {
 			$dataLocation = false;
 		}
 
@@ -198,7 +198,7 @@ class JSConfigHelper {
 
 		$array = [
 			"_oc_debug" => $this->config->getSystemValue('debug', false) ? 'true' : 'false',
-			"_oc_isadmin" => $this->groupManager->isAdmin($uid) ? 'true' : 'false',
+			"_oc_isadmin" => $uid !== null && $this->groupManager->isAdmin($uid) ? 'true' : 'false',
 			"backendAllowsPasswordConfirmation" => $userBackendAllowsPasswordConfirmation ? 'true' : 'false',
 			"oc_dataURL" => is_string($dataLocation) ? "\"" . $dataLocation . "\"" : 'false',
 			"_oc_webroot" => "\"" . \OC::$WEBROOT . "\"",
diff --git a/lib/public/IGroupManager.php b/lib/public/IGroupManager.php
index f8f0a5c47c..eec36f3de7 100644
--- a/lib/public/IGroupManager.php
+++ b/lib/public/IGroupManager.php
@@ -112,10 +112,10 @@ interface IGroupManager {
 
 	/**
 	 * @param \OCP\IUser $user
-	 * @return array with group names
+	 * @return string[] with group names
 	 * @since 8.0.0
 	 */
-	public function getUserGroupIds(IUser $user);
+	public function getUserGroupIds(IUser $user): array;
 
 	/**
 	 * get a list of all display names in a group
diff --git a/tests/lib/Group/ManagerTest.php b/tests/lib/Group/ManagerTest.php
index 8b6be03615..dfe21b825f 100644
--- a/tests/lib/Group/ManagerTest.php
+++ b/tests/lib/Group/ManagerTest.php
@@ -395,6 +395,7 @@ class ManagerTest extends TestCase {
 		 */
 		$backend = $this->getTestBackend();
 		$backend->method('getUserGroups')
+			->with('myUID')
 			->willReturn(['123', 'abc']);
 
 		$manager = new \OC\Group\Manager($this->userManager, $this->dispatcher, $this->logger);
@@ -402,6 +403,8 @@ class ManagerTest extends TestCase {
 
 		/** @var \OC\User\User|\PHPUnit\Framework\MockObject\MockObject $user */
 		$user = $this->createMock(IUser::class);
+		$user->method('getUID')
+			->willReturn('myUID');
 
 		$groups = $manager->getUserGroupIds($user);
 		$this->assertCount(2, $groups);