PHP Notice: Undefined variable: args in class-simple-settings.php on line 1339
1.2.0 and higher introduces a nonce check in process_actions(), however this is referencing an $args array that isn't declared: https://gitlab.com/widgitlabs/wordpress/simple-settings/-/blob/1.2.0/class-simple-settings.php#L1338
This isn't present in 1.0.1: https://gitlab.com/widgitlabs/wordpress/simple-settings/-/blob/1.0.1/class.simple-settings.php#L1281
As a result, a PHP warning is shown (specifically, in WordPress' Username Changer Plugin 3.2.1, which uses Simple Settings 1.2.1)