MC-35119: U2F Key registration error in Chrome on Ubuntu

Author: nathanjosiah

TwoFactorAuth/Model/Provider/Engine/U2fKey/WebAuthn.php

@@ -298,7 +298,9 @@ public function getPublicKeyFromRegistrationData(array $data): array
         return [
             'key' => $attestationObject['attestationData']['keyBytes'],
             'id' => $credentialData['id'],
-            'aaguid' => base64_encode($attestationObject['attestationData']['aaguid']) ?? null
+            'aaguid' => empty($attestationObject['attestationData']['aaguid'])
+                ? null
+                : base64_encode($attestationObject['attestationData']['aaguid'])
         ];
     }