White space on top of admin because of unseen PHP error

[bfintal]

🐞 bug report

Behavior:

• What is the issue? (*)
  In the admin, I see this white space at the top, which is caused by a PHP error coming from the Freemius SDK.

If you print the last error in PHP, you'll see this error:

Creation of dynamic property FS_User::$is_beta is deprecated

• What is the expected behavior?

No error, no white space