The function alloc_ctrl_packet() can fail and return NULL. Incase it
fails print an error message and exit.
Signed-off-by: NSudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Reviewed-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>