No-op CastSessionIdMap when group_id is disabled

The audio group id will be null when kAudioServiceAudioStream is
disabled, so we No-op the CastSessionIdMap calls.

Bug: 121270801
Test: cast_shell_unittests
Change-Id: I8bb6d56c79d4d98ea255c48b9eaf50322a7523c2
Reviewed-on: https://chromium-review.googlesource.com/c/1404474
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Aidan Wolter <awolter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622225}
5 files changed