A workaround for an NSFetchedResultsController bug introduced in XCode 7. Credits to stackoverflow user Andy: http://stackoverflow.com/a/32466951/809614

frchack.swift

// Workaround a nasty bug introduced in XCode 7 targeted at iOS 8 devices
// https://forums.developer.apple.com/message/9998#9998
// https://forums.developer.apple.com/message/31849#31849
// This is not my original idea. Please give your stars to stackoverflow user Andy for sharing his solution: http://stackoverflow.com/a/32466951/809614

class MyFetchedResultsControllerDelegate: NSObject, NSFetchedResultsControllerDelegate {
    
    // ... your code
    
    // MARK: Private
    
    // These two Sets let us track changes in the sections so we can use them for analysis later on
    private var deletedSections = Set<Int>()
    private var insertedSections = Set<Int>()

    // MARK: NSFetchedResultsControllerDelegate
    
    @objc dynamic func controllerWillChangeContent(controller: NSFetchedResultsController) {
        
        // Very important to clear these. You can also probably do this in controllerDidChangeContent(_:)
        self.deletedSections = []
        self.insertedSections = []
        
        // handle normally
    }
    
    @objc dynamic func controllerDidChangeContent(controller: NSFetchedResultsController) {
        
        // handle normally here
    }
    
    @objc dynamic func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
        
        if #available(iOS 9, *) {
            
            // iOS 9 is immune to this bug. handle normally here
            return
        }
        
        switch type {
            
        case .Move:
            guard let indexPath = indexPath, let newIndexPath = newIndexPath else {
                
                return // This shouldn't happen either way and should be fine to just force-unwrap, but just for safe measure.
            }
            if indexPath == newIndexPath
                && self.deletedSections.contains(indexPath.section) {
                    
                    // This is where we get our crash:
                    // - The indexPath.section was already deleted so we have no business to move it to newIndexPath.section (which our if-statement checked to be equal with itself)
                    // - What we do then is treat this case as an ".Insert"
                    
                    // handle as ".Insert" here
                    return
            }
            
        case .Update:
            guard let section = indexPath?.section else {
                
                return // This shouldn't happen either way and should be fine to just force-unwrap, but just for safe measure.
            }
            if self.deletedSections.contains(section)
                || self.insertedSections.contains(section) {
                    
                    // This indexPath's section was either deleted or inserted, so we have no business updating it.
                    // Ignore this notification and wait for the upcoming ".Move" notification which we will treat as a ".Insert"
                    return
            }
            
        default: // other cases are fine, just handle normally
            break
        }
        
        // handle normally here
    }
    
    @objc dynamic func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
        
        switch type {
            // Very important. We'll use these info for analysis later.
        case .Delete:   self.deletedSections.insert(sectionIndex)
        case .Insert:   self.insertedSections.insert(sectionIndex)
        default: break
        }
        
        // handle normally here
    }
    
    @objc dynamic func controller(controller: NSFetchedResultsController, sectionIndexTitleForSectionName sectionName: String) -> String? {
        
        // handle normally here
    }

}