update

web/core/modules/basic_auth/src/Authentication/Provider/BasicAuth.php

@@ -128,7 +128,7 @@ class BasicAuth implements AuthenticationProviderInterface, AuthenticationProvid
     }
     // Always register an IP-based failed login event.
     $this->flood->register('basic_auth.failed_login_ip', $flood_config->get('ip_window'));
-    return [];
+    return NULL;
   }
 
   /**

web/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php

@@ -76,7 +76,7 @@ class BasicAuthTest extends BrowserTestBase {
 
     // Ensure that a route without basic auth defined doesn't allow login.
     $this->basicAuthGet(Url::fromRoute('system.admin'), $account->getAccountName(), $account->pass_raw);
-    $this->assertNoLink('Log out', 'User is not logged in');
+    $this->assertSession()->linkNotExists('Log out', 'User is not logged in');
     $this->assertSession()->statusCodeEquals(403);
     $this->mink->resetSessions();