What's the proper way to handle disconnections in UNET?

I'm making a two player card game using the matchmaker, and I can't figure out how to properly delete matches from the matchmaker, and how to handle a case like when the user creates a match and then changes their mind and backs out to the create match dialogue (implemented as a panel that I enable and disable).
Here's what I've tried so far:
What's the proper way to handle disconnections in UNET?