notificationCenter.postNotificationName(NotificationContactCreated, object: nil) fatal error - ios

Question

I have this line of code that successfully runs on first got:
notificationCenter.postNotificationName(NotificationContactCreated, object: nil)
But later on when this same line in same function is called I get the fatal error:
fatal error: unexpectedly found nil while unwrapping an Optional value
Yet if I set through the code both notificationCenter and NotificationContactCreated are both set.
I'm going round in circles and cannot find the cause of this...
Any help ...please???
Thanks
here is the notification center:
//
// notification center to be used across phone app
//
lazy var notificationCenter: NSNotificationCenter = {
return NSNotificationCenter.defaultCenter()
}()
here is the func where it gets called:
func updateAccount(firstName: String, lastName: String, emailAddress: String, companyName: String, isSelf: Bool) -> Void {
// we are going to update the Contacts entity
let fetchRequest = NSFetchRequest(entityName: entityNameContacts)
// filter on first name + last name + email address
fetchRequest.predicate = NSPredicate(format: "firstName == %# && lastName == %# && emailAddress == %#", firstName, lastName, emailAddress)
do {
// try to get an array of accounts based on filter, should only be one returned
let contactsArray = try context.executeFetchRequest(fetchRequest) as? [Contacts]
// if there is a record we just want to update it
if contactsArray?.count > 0 {
// grab the reading object
let contact = contactsArray![0]
// and update its data
contact.firstName = firstName
contact.lastName = lastName
contact.emailAddress = emailAddress
contact.companyName = companyName
}
else {
// otherwise we need to insert a new record
let newContact: Contacts = NSEntityDescription.insertNewObjectForEntityForName(entityNameContacts, inManagedObjectContext: context) as! Contacts
// and populate with new data
newContact.firstName = firstName
newContact.lastName = lastName
newContact.emailAddress = emailAddress
newContact.companyName = companyName
newContact.isSelf = isSelf
}
// write amends
saveContext()
self.notificationCenter.postNotificationName(NotificationContactCreated, object: nil)
} catch {
print("func updateAccount(firstName: String, lastName: String, emailAddress: String, companyName: String, isSelf: Bool) -> Void !!!ERROR")
}