[advertising-proxy] fix dereferencing `aUpdate` (#1243)
[advertising-proxy] fix dereferencing `aUpdate` (#1243)


openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix