jdg/MBProgressHUD — pull request #188 by Arcnor (2014-01-23 21:52:33+00:00)
Title: When calling multiple show: and hide: too fast, some of the HUDs can get stuck

The problem is, when hiding, we only hide the first HUD in the list, but that one can be in the process of being deleted, but not finished yet (because it's animating or any other cause). My fix gets the first non-hiding HUD and uses that one instead.