UISearchDisplayController inside popover - bad animation on cancelling search

My iPad app uses a popover to perform some searching. The search results are handled using a UISearchDisplayController, and I am having some trouble removing some little graphical artefacts.

My popover starts out looking like this:

When you click inside the search bar, the popover expands (animat开发者_如何转开发ed) to:

All good so far... typing in the search field overlays a new table view showing the results of your search term.

But if you don't type anything into the search field, the overlay stays translucent, as above. The problem then comes when you click the cancel button next to the search field. A visual artefact appears at the bottom of the table view: an area the same height as one of the table view cells goes completely clear immediately, while the rest of the overlay animates to 0 alpha. The screenshot below is as close to the start of the animation I could get:

The popover also resizes to the original size in my case, although the artefact remains even if there is no resizing.

Given that all the important functionality of the search is handled by the UISearchDisplayController, I'm not sure what to change to solve this problem. Any ideas?

This might be a bug worth reporting. There are actually a surprising number of bugs in UIPopoverController. At least 3 that I know about separate from this, none of which are planned to be fixed anytime soon (I asked several engineers at WWDC this year). One of my bugs was actually related to the UISearchDisplayController in a popover, specifically how it handles filter buttons if the Popover is in the detail view (it renders them in the worst possible way, on the same line as the text view and completely unusable).