Fix potenial NPE in PhonePolicy

NPE might happen in PhonePolicy since HeadsetService could be null.

Bug: 65842557
Fixes: 65842557
Test: Connect Bluetooth devices and check A2DP/HeadSet profiles

Change-Id: Ib90147b407bc80675ba027f4c6cac94ae39a1d7b
Signed-off-by: xutianguo <xutianguo@xiaomi.com>
(cherry picked from commit eb2e3473)