Fix do not unregister bluetooth receiver if it was not registered

Bug: webrtc:7890
Change-Id: Ib46b4a4407fa030500930ed03a093b26c71f8963
Reviewed-on: https://chromium-review.googlesource.com/550617
Commit-Queue: Henrik Andreasson <henrika@webrtc.org>
Reviewed-by: Henrik Andreasson <henrika@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18892}
diff --git a/AUTHORS b/AUTHORS
index cb537cf..3a17351 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -19,6 +19,7 @@
 Frederik Riedel, Frogg GmbH <frederik.riedel@frogg.io>
 Giji Gangadharan <giji.g@samsung.com>
 Graham Yoakum <gyoakum@skobalt.com>
+Gustavo Garcia <gustavogb@gmail.com>
 Hugues Ekra <hekra01@gmail.com>
 Jake Hilton <jakehilton@gmail.com>
 James H. Brown <jbrown@burgoyne.com>