[DO NOT MERGE] Move AuthSession usage to after null check

The system already schedules anything that reads/modifies/writes
AuthSession on the handler, so there shouldn't be any race condition
that can cause this. Simply move the session reading to after
the null check.

Fixes: 159897806

Test: Builds
Change-Id: Ia4c3ce32e9af3e8b73c02f5eab969f7314afc4c8