Filing a Bug Against Core Graphics [Update: fixed]

So, I was verifying that my Chemistry Keyboard works with the iOS 12 beta, and I immediately noticed that the Globe button's icon looked like this:

As I render all my artwork with my own SVGgh library, I had stumbled across a bug in Core Graphics. After much checking and simplifying I figured out that it was possible to add an arc to a CGMutablePath with parameters such that a subsequent call to CGPathCloseSubpath would not maintain the path's current point, and instead revert it to (0.0, 0.0). 

Filed a bug (42266130) with the Apple bug reporter and I hope they can get around to fixing it by release. 

[Update: Fixed in the 5th beta. Thanks for the responsiveness.]