fix(data-source): Wait until the next cycle to cleanup
fix(data-source): Wait until the next cycle to cleanup

Fixes a crash when switching to the thread list from the draft list, where there are very briefly zero observers.

nirmit/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail