[Rust] Transport with only audio producer results in server-side transport cc is not created.

[mstyura]

Bug Report

WebRtcTransport with only audio producer with enabled transport congestion control results in transport CC is not actually enabled on server side, i.e. Transport::tccServer is nullptr

Your environment

• Operating system: -
• Node version: -
• npm version: -
• gcc/clang version: -
• mediasoup version: v3.13.24
• mediasoup-client version: -

Issue description

Steps to reproduce:

1. Run rust/examples/echo
2. Edit rust/examples-frontend/echo/src/index.ts to disable video and hence video producer
3. Run rust/examples-frontend/echo
4. Open echo app in browser http://localhost:3001/

Actual result:

Bitrate of sent audio is started at high values and drops to minimum allowed by webrtc (16Kb/s).

Expected result:

Bitrate of sent audio is depend on actual network bandwidth available.

[ibc]

Please paste the browser side SDP after creating the audio Producer and also the RtpParameters given to transport.produce() in server side.

[mstyura]

I've found an issue and will provide MR with fix, this was just a justification issue to link with MR.