Fix usage of Session::unserialize()
Fix usage of Session::unserialize()

This function should be checking new value for emptiness, but it was checking
the database value instead. Additionally, at this point, the database value
would always be `NULL`. Changed to use the correct variable.

BloodBrother/symphony-2,alexnantel88/symphony-2,alexnantel88/symphony-2,BloodBrother/symphony-2