fix(config): don’t try to unsubscribe if no subscription
fix(config): don’t try to unsubscribe if no subscription

Fixes #270
Closes #271

ng-lightning/ng-lightning,ihym/ng-lightning,dballance/ng-lightning,ng-lightning/ng-lightning,ihym/ng-lightning,esarbanis/ng-lightning,ppolyzos/ng-lightning,ihym/ng-lightning,dballance/ng-lightning,esarbanis/ng-lightning,ppolyzos/ng-lightning,dballance/ng-lightning,esarbanis/ng-lightning,ppolyzos/ng-lightning