fix buttons not showing up in iOS8

With Xcode6 beta and the iOS8 simulator, the buttons do not show and you get Layout Constraints exceptions. This is due to rowHeight of both suggestedButtonTableView and otherButtonsTableView being -1.

Not sure if there's a better way to fix this or even if this is a bug in iOS8, but for now this fixes it for me and makes my app work again in iOS8