a2dp: Fix invalid memory access during abort_ind()

a2dp: Fix invalid memory access during abort_ind()

There is an invalid memory access w.r.t to the callback
during the Abort_Ind finalize_setup_errno().

We should terminate the variable arguments with NULL.

Log:
bluetoothd[3353]: audio/avdtp.c:avdtp_parse_cmd() Received ABORT_CMD
bluetoothd[3353]: audio/a2dp.c:abort_ind() Source 0xb6f5ecc8: Abort_Ind
bluetoothd[3353]: audio/a2dp.c:setup_ref() 0xb6f63200: ref=2
bluetoothd[3353]: audio/transport.c:media_transport_remove() Transport
 /org/bluez/3353/hci0/dev_BC_47_60_F5_88_89/fd1 Owner :1.0
bluetoothd[3353]: audio/transport.c:media_transport_release() Transport
 /org/bluez/3353/hci0/dev_BC_47_60_F5_88_89/fd1: read lock released
bluetoothd[3353]: audio/transport.c:media_transport_release() Transport
 /org/bluez/3353/hci0/dev_BC_47_60_F5_88_89/fd1: write lock released
bluetoothd[3353]: audio/transport.c:media_request_reply() Request
 Acquire Reply Input/output error
bluetoothd[3353]: audio/transport.c:media_owner_free() Owner :1.0
bluetoothd[3353]: audio/transport.c:media_owner_remove() Owner :1.0 Request Acquire
bluetoothd[3353]: audio/a2dp.c:a2dp_sep_unlock() SEP 0xb6f5ecc8 unlocked
bluetoothd[3353]: audio/a2dp.c:setup_unref() 0xb6f63200: ref=1
[sys_assert]START of sighandler
[sys-assert]exepath = bluetoothd
[sys-assert]processname = bluetoothd
[sys_assert]this thread is main thread. pid=3353
[sys-assert]cs timestr 1358524835
bluetoothd[3353]: crashed [1358524835] processname=bluetoothd, pid=3353, tid=3353, signal=11
[sys-assert]start print_node_to_file
sighandler = 0xb6e8cfc9, g_sig_oldact[i] = (nil)
[sys_assert]END of sighandler
Segmentation fault (core dumped)