recipient_change hook throws console errors when compose is closed

[arturs-buls]

Summary

recipient_change errors out when compose, that has recipients, gets closed.

Steps to reproduce

1. Setup recipient_change observer
2. Open compose. Put some recipient in.
3. Close that compose
4. Observe gmail-inject.js:8009 Can't find composeRoot for [object Object] and api.dom.compose called with invalid element thrown in console

Stack trace

gmail-inject.js:8009 Can't find composeRoot for [object Object]
Gmail.api.tools.error @ gmail-inject.js:8009
(anonymous) @ gmail-inject.js:9372
setTimeout (async)
handler @ gmail-inject.js:9363
(anonymous) @ gmail-inject.js:9321
each @ gmail-inject.js:431
Gmail.api.observe.trigger_dom @ gmail-inject.js:9320
(anonymous) @ gmail-inject.js:9478

gmail-inject.js:8009 api.dom.compose called with invalid element
Gmail.api.tools.error @ gmail-inject.js:8009
Gmail.api.dom.compose @ gmail-inject.js:10446
(anonymous) @ gmail-inject.js:9374
setTimeout (async)
handler @ gmail-inject.js:9363
(anonymous) @ gmail-inject.js:9321
each @ gmail-inject.js:431
Gmail.api.observe.trigger_dom @ gmail-inject.js:9320
(anonymous) @ gmail-inject.js:9478

I guess it might be some race condition, due to setTimeout, but maybe there is a way to check if compose still exist in setTimeout callback?