Backgrounding fakewallet in the middle of a session should close the session

[steveluscher]

Repro:

1. Open the example web app
2. Exercise the ‘record message’ feature
3. Without signing the transaction in the wallet, context switch back to the browser

Observe that the websocket connection is still active and the app is still waiting for an answer from the wallet. In my opinion, aborting a session by backgrounding the wallet should be equivalent to cancelling the session.