Only update match if editor is still alive
Only update match if editor is still alive

Previously this wasn't guarding against the last possible cursor being
destroyed in which case update match should not be performed when the
editor is no longer alive.

Closes #35

adamCoGithub/Bracket-Matcher-no-smart-quotes,lpommers/bracket-matcher,adamCoGithub/Bracket-Matcher-no-autoclose,bwinton/bracket-matcher,atom/bracket-matcher,lpommers/bracket-matcher,jacekkopecky/bracket-matcher,adamCoGithub/Bracket-Matcher-no-autoclose,bwinton/bracket-matcher,adamCoGithub/Bracket-Matcher-no-smart-quotes,jacekkopecky/bracket-matcher