OUIViewController asserts precondition unretained_prospective_parent?

[memmons]

In OUIViewController there is an OBPRECONDITION that requires unretained_prospective_parent to not be nil (see below). However, this will be nil in some cases. For example, using an OUIScalingViewController subclass in a view controller embedded in a nav controller via storyboard. In this case, willMoveToParentViewController is never called, which is where _unretained_prospective_parent is initially being set.

- (void)didMoveToParentViewController:(UIViewController *)parent;
{
    DEBUG_PARENT_VC(@"In %s with parent: %@", __func__, parent);
    OBPRECONDITION(parent == _unretained_prospective_parent);
    ...
    _unretained_parent = parent;
}