fix(composer): Add additional isMounted checks
fix(composer): Add additional isMounted checks

Resolves this exception: https://gist.github.com/jstejada/a26dc6a7a2896dcef9be3cec60eaecdb

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