AVRCP: Fix crash while listing available settings in TG role
AVRCP: Fix crash while listing available settings in TG role

Invalid read of size 1
   at 0x41AFD0: attrval_to_val (avrcp.c:492)
   by 0x41B0E1: avrcp_handle_list_player_attributes (avrcp.c:931)
   by 0x41D606: handle_vendordep_pdu (avrcp.c:1620)
   by 0x4185F8: session_cb (avctp.c:985)
   by 0x3F31A47A54: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x3F31A47D87: ??? (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x3F31A48181: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x40A2E5: main (main.c:595)
 Address 0x0 is not stack'd, malloc'd or (recently) free'd

mapfau/bluez,pkarasev3/bluez,pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez,pkarasev3/bluez,pkarasev3/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,silent-snowman/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez