Web client participants not removed when tab closed

[jansch]

Description/Error

We allow participants to join meetings via the web client, i.e. via subdomain.zoom.us/wc/join/... Most of the time participants do not actively "Leave" a meeting but simply close the tab of their browser. While their audio and video naturally does not get transmitted anymore, they are still displayed as a participant in the call. For several obvious reasons that is an issue:

• Network issues might cause the participant to drop out and re-enter resulting in duplicated participant
• Faulty participant tracking
• Difficult to tell if participants left or have issues with their audio/video

How To Reproduce (If applicable)
Create meeting. Enter via web client and as host via desktop app. Close browser tab. Observe that participant is still part of the meeting.