self.parentViewController is valid on first execution, but nil thereafter - ios

Question

I have some code that builds and displays a viewController inside a navigation controller. The first time through the handleDoubleTapRecognizer everything works as expected. However, EVERY time thereafter that handleDoubleTapRecognizer is triggered, the navigation controller and its content controller, built in the handleDoubleTapRecognizer never appear, and instead I get this delightful message in the console...
Warning: Attempt to present <UINavigationController: 0x7bbafa00> on <iRpImageViewerViewController: 0x80164580> whose view is not in the window hierarchy!
Also note that [self.view superview] returns nil, so something is totally destroying the connections from this view to its parent.
...
#implementation iRpImageViewerViewController
{
IGGridView *theMainImageGridviewControl;
iRpImageSet *thePropertyImageSet;
iRpImageFilmstripViewController *theFilmstripViewController;
iRpImageAndMedia *initialMediaItem; // The item to display when first loaded.
UIImageView *primaryImageMarker;
UINavigationController *imageEditorNavController;
iRpImageEditorViewController *imageEditorVC;
}
...
-(void)handleDoubleTapRecognizer:(UITapGestureRecognizer*)recognizer
{
NSLog(#"Double Tapped on ImageViewerViewController's main image, so opening editor");
IGCellPath *pathForCurrentCell = [self pathForCurrentCell];
iRpImageAndMedia *imageAndMediaItem = [thePropertyImageSet objectAtIndex:pathForCurrentCell.columnIndex];
imageEditorVC = [[iRpImageEditorViewController alloc] initWithImageAndMediaItem:imageAndMediaItem];
imageEditorVC.navigationItem.title = #"Photo Details Editor";
imageEditorVC.edgesForExtendedLayout = UIRectEdgeNone;
imageEditorNavController = [[UINavigationController alloc] initWithRootViewController:imageEditorVC];
imageEditorNavController.modalPresentationStyle = UIModalPresentationFormSheet;
imageEditorNavController.topViewController.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:#selector(imageEditorDone)];
imageEditorNavController.topViewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:#selector(imageEditorCancelled)];
imageEditorNavController.preferredContentSize = imageEditorVC.view.frame.size;
NSLog(#"%#'s parentViewController is %#",self, self.parentViewController);
[self presentViewController:imageEditorNavController animated:YES completion:^(void){ }];
}
-(void)imageEditorDone
{
[self dismissViewControllerAnimated:YES completion:nil];
}
-(void)imageEditorCancelled
{
[self dismissViewControllerAnimated:YES completion:nil];
}