Fix 'Variable assignment found within a condition. Did you mean to do a comparison ?' issue in src\SessionStorage.php

[CodeFactor](https://www.codefactor.io/repository/github/baraja-core/session) found an issue: Variable assignment found within a condition. Did you mean to do a comparison ?

It's currently on:
[src\SessionStorage.php:154](https://www.codefactor.io/repository/github/baraja-core/session/source/master/src/SessionStorage.php#L154)

The reported location is src/SessionStorage.php:154; inspect the condition and surrounding logic first to determine whether the assignment is intentional or should be a comparison. Confirm the CodeFactor warning is gone and existing session-storage behavior remains unchanged.

Written by the indexing model from the issue text.