Migrate Persistant Store Crash

I have a switch that turns iCloud on or off for an iOS 7 app. iCloud sync works fine. When iCloud is on and I turn it off, I call this code:

- (void)migrateiCloudStoreToLocalStore {

NSError *error;

__weak NSPersistentStoreCoordinator *psc = self.managedObjectContext.persistentStoreCoordinator;

NSDictionary *options = @{NSMigratePersistentStoresAutomaticallyOption:@YES,
                          NSPersistentStoreRemoveUbiquitousMetadataOption : @YES};

NSPersistentStore *currentStore = [psc persistentStores][0];

NSLog(@"iCloud Store - %@", currentStore);

NSLog(@"Local Store - %@", self.store);

[psc migratePersistentStore:currentStore
                      toURL:self.store
                    options:options
                   withType:NSSQLiteStoreType
                      error:&error];

}

I can see that both stores do exist but it still crashes when migratePersistentStore:toURL:options:withType:error: is called.

Here's the error I get:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM replaceObjectAtIndex:withObject:]: object cannot be nil' *** First throw call stack: (0x2e0a3fd3 0x38850ccf 0x2dfdf29f 0x2de9e7f7 0xa9b61 0xb2305 0xb019f 0x309de05f 0x30a90377 0x3093f6f5 0x308b855b 0x2e06f2a5 0x2e06cc49 0x2e06cf8b 0x2dfd7f4f 0x2dfd7d33 0x32edc663 0x3092316d 0x30289 0x38d5dab7) libc++abi.dylib: terminating with uncaught exception of type NSException

Any idea why this is happening? It's a bit odd because on one of my other devices, it doesn't crash at this point.

Try This

[psc removePersistentStore:currentStore error:nil];

[psc migratePersistentStore:currentStore
                      toURL:self.store
                    options:options
                   withType:NSSQLiteStoreType
                      error:&error];

[psc addPersistentStoreWithType:NSSQLiteStoreType
                  configuration:nil
                            URL:self.store
                        options:options /* options for local store */
                          error:nil];

UPDATE: new solution

NSPersistentStoreCoordinator * persistentStoreCoordinator = self.persistentStoreCoordinator;

NSPersistentStore * persistentStore = [[persistentStoreCoordinator persistentStores] firstObject];

NSMutableDictionary * localStoreOptions = [[self localPersistentStoreOptions] mutableCopy];

[localStoreOptions setObject:@YES forKey:NSPersistentStoreRemoveUbiquitousMetadataOption];

[[NSFileManager defaultManager] copyItemAtPath:persistentStore.URL.path toPath:[self storeURL].path error:nil];

NSPersistentStoreCoordinator * newPersistentStoreCoordinator;

newPersistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

[newPersistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType

                                            configuration:nil

                                                      URL:[self storeURL]

                                                  options:localStoreOptions

                                                    error:nil];

[self setPersistentStoreCoordinator:newPersistentStoreCoordinator];

[self setupManagedObjectContext]; //initialize new moc with new persistent store coordinator