AVRCP_Browse: fix NPE issue while check MBS connect in BrowseMediaPlayer

Add check null condition for handler while check MBS connect in BrowseMediaPlayer.
And initialize the handler thread in Avrcp start during BT On time rather than
Conditional initialization to avoid mHandler as NULL

Change-Id: I884235507e41140c6ec41c66e1bff40f0d42f927
CRs-Fixed: 2564405
2 files changed