There is a discussion in WebRTC 1.0 about the effect of setting sender.track to null (see Issue w3c/webrtc-pc#943).
Same Issue applies to ORTC.
Effect of sender.track set to null
Fix for Issue #616.
Related to WebRTC 1.0 PR w3c/webrtc-pc#944
Add change log
Added change log for Issues #615 and #616.