Fix fault has not been fired when adding a new doc from sync
Fix fault has not been fired when adding a new doc from sync

* Fixed NSIncrementalStore not firing fault when adding a new document from sync. The solution (calling willAccessValueForKey: method with nil value on an NSManagedObject) to ensure that fault is firing was suggested by https://github.com/couchbase/couchbase-lite-ios/pull/383 posted by @Rostmen. The solution is inline with what Apple suggests in the willAccessValueForKey: API doc.

* Fixed crash when deleting an nsmanaged object.

#576

amco/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,alfared/couchbase-lite-ios,brendand/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,Chavenay/couchbase-lite-ios,lordkev/couchbase-lite-ios,lordkev/couchbase-lite-ios,Chavenay/couchbase-lite-ios,pegli/couchbase-lite-ios,alfared/couchbase-lite-ios,couchbase/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,macoscope/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,lordkev/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,macoscope/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,macoscope/couchbase-lite-ios,lordkev/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,Chavenay/couchbase-lite-ios,pegli/couchbase-lite-ios,alfared/couchbase-lite-ios,amco/couchbase-lite-ios,pegli/couchbase-lite-ios,couchbase/couchbase-lite-ios,macoscope/couchbase-lite-ios,couchbase/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,couchbase/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,tomco/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,tomco/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,amco/couchbase-lite-ios,tomco/couchbase-lite-ios,amco/couchbase-lite-ios,tomco/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,pegli/couchbase-lite-ios,alfared/couchbase-lite-ios,amco/couchbase-lite-ios