iOS: UIDatePicker causing "UITableView dataSource is not set"?

Question

I have a UIDatePicker inside a UIViewController, and in some rare cases I am getting this Exception:

Fatal Exception: NSInternalInconsistencyException
UITableView dataSource is not set
0  CoreFoundation                 0x1820badb0 __exceptionPreprocess
1  libobjc.A.dylib                0x18171ff80 objc_exception_throw
2  CoreFoundation                 0x1820bac80 +[NSException raise:format:]
3  Foundation                     0x182a40154 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
4  UIKit                          0x18756efe0 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:]
5  UIKit                          0x18756f198 -[UITableView _createPreparedCellForGlobalRow:willDisplay:]
6  UIKit                          0x18755e468 -[UITableView _updateVisibleCellsNow:isRecursive:]
7  UIKit                          0x187573c64 -[UITableView _performWithCachedTraitCollection:]
8  UIKit                          0x1873048c4 -[UITableView layoutSubviews]
9  UIKit                          0x18794aa38 __35-[UIPickerTableView layoutSubviews]_block_invoke
10 UIKit                          0x1872275b4 +[UIView(Animation) performWithoutAnimation:]
11 UIKit                          0x18794a9c4 -[UIPickerTableView layoutSubviews]
12 UIKit                          0x1872141e4 -[UIView(CALayerDelegate) layoutSublayersOfLayer:]
13 QuartzCore                     0x184ba6994 -[CALayer layoutSublayers]
14 QuartzCore                     0x184ba15d0 CA::Layer::layout_if_needed(CA::Transaction*)

This is the code of the UIViewController:

import UIKit

protocol PickerViewProtocol {
    func onSearchDateChange (date: NSDate)
}


class PickerViewController: UIViewController {

    @IBOutlet weak var datePicker: UIDatePicker!

    var initDate : NSDate?
    var delegate : PickerViewProtocol?


    override func viewDidLoad() {
        //print("PickerViewController viewDidLoad")
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        datePicker.timeZone = NSTimeZone(name: "Europe/Rome")
        if initDate != nil {
            datePicker.date = initDate!
        }
        datePicker.addTarget(self, action: #selector(PickerViewController.datePickerChanged(_:)), forControlEvents: UIControlEvents.ValueChanged)
    }

    func setDate(date:NSDate) {
        if datePicker != nil {
            datePicker.date = date
        } else {
            initDate = date
        }
    }


    func datePickerChanged(datePicker:UIDatePicker) {
        delegate?.onSearchDateChange(datePicker.date)
    }


}