Deprecated error on isOauth1 function using php8.1

[dlopez-akalam]

The \Mautic\Auth\OAuth::isOauth1() method is potentially being called before the _request_token_url attribute is initialized. As result, a NULL value is passed to the strlen() php function, causing a deprecation warning.

Deprecated function: strlen(): Passing null to parameter #1 ($string) of type string is deprecated in Mautic\Auth\OAuth->isOauth1() (line 525 of /.../vendor/mautic/api-library/lib/Auth/OAuth.php).
Mautic\Auth\OAuth->isOauth1() (Line: 564)
Mautic\Auth\OAuth->prepareRequest('https://mautic.example.com/api/forms', Array, Array, 'GET', Array) (Line: 115)
Mautic\Auth\AbstractAuth->makeRequest('https://mautic.example.com/api/forms', Array, 'GET', Array) (Line: 259)
Mautic\Api\Api->makeRequest('forms', Array) (Line: 399)
Mautic\Api\Api->getList('', 0, 100, '', 'ASC', 1, 1) (Line: 234)