[BUG]: end of candidates indicator

Package version

3.0.0-pre.6

Environment

* OS: Windows 10
* Unity version: 2022.3.5f1

Steps To Reproduce

I'm able to connect to gstreamer signalling server, and connect to audio/video producers. Local tests work well.

In real conditions, with two different computers, I receive from the gstreamer producer that makes the SDP offer a null ice candidate {"type":"peer","sessionId":"c375043d-1145-4867-99de-97ed0240b898","ice":{"candidate":"","sdpMLineIndex":0}}. I believe this is supposed to mean the end of the sending of ice candidates (end of candidates indicator)

Current Behavior

Unity fails to make an empty ice candidate

ArgumentException: create candidate is failed. error type:InvalidParameter, candidate:
sdpMid:
sdpMLineIndex:0
  at Unity.WebRTC.RTCIceCandidate..ctor (Unity.WebRTC.RTCIceCandidateInit candidateInfo) [0x000c1] in .\Library\PackageCache\com.unity.webrtc@3.0.0-pre.6\Runtime\Scripts\RTCIceCandidate.cs:264 

I am supposed to simply ignore this ice candidate? (if I do so the connection if ended by gstreamer but I don't know exactly why yet)

Expected Behavior

This case should be managed by Unity. For now this function is designed to refuse any empty candidate

        public RTCIceCandidate(RTCIceCandidateInit candidateInfo = null)
        {
            candidateInfo = candidateInfo ?? new RTCIceCandidateInit();
            if(candidateInfo.sdpMLineIndex == null && candidateInfo.sdpMid == null)
                throw new ArgumentException("sdpMid and sdpMLineIndex are both null");

            RTCIceCandidateInitInternal option = (RTCIceCandidateInitInternal)candidateInfo;
            RTCErrorType error = NativeMethods.CreateIceCandidate(ref option, out self);
            if (error != RTCErrorType.None)
                throw new ArgumentException(
                        $"create candidate is failed. error type:{error}, " +
                        $"candidate:{candidateInfo.candidate}\n" +
                        $"sdpMid:{candidateInfo.sdpMid}\n" +
                        $"sdpMLineIndex:{candidateInfo.sdpMLineIndex}\n");

            NativeMethods.IceCandidateGetCandidate(self, out _candidate);
        }
    }

Anything else?

No response