Return type of the restoreToken function, in the TokenPersistenceInterface can't be null

[GabGr25]

We can see here, the restoreToken function must return sometimes null.

But in the TokenPersistenceInterface, we can see the return type of the function restoreToken is just TokenInterface.

An example, in this implementation of the TokenPersistenceInterface, where the return type is null.

I create this issues because i have a Psalm error.

[kamermans]

Good point, I'll release this shortly!