ArgumentNullException when receiving RE-INVITE request

[vezhichenko]

Is it possible to process re-invite requests without SDP? My server sends such a request when I try to put SIPUserAgent on remote hold.

I found a section of code that is responsible for this logic in the "DialogRequestReceivedAsync" method.

// ignored, because _oldCallId == null
if (sipRequest.Header.CallId == _oldCallID)
{
    SDP sDP = MediaSession.CreateAnswer(null);
    SIPResponse okResponse = reInviteTransaction.GetOkResponse("application/sdp", sDP.ToString());
    reInviteTransaction.SendFinalResponse(okResponse);
    return;
}

// sessionDescription == null => ArgumentNullException
SetDescriptionResultEnum setDescriptionResultEnum = MediaSession.SetRemoteDescription(SdpType.offer, sessionDescription);

[sipsorcery]

Reaolved in #1234.