Bluetooth: Check returned buffer is not NULL

Buffers returned by bt_uart_evt_recv() and bt_uart_acl_recv() may be
NULL in theory. This makes code consistent by checking return value.

Change-Id: Id39def39c8b1c4c6eefc7b2bf01702c54b3e565c
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
1 file changed