deleteRowsAtIndexPath crash (reproducible in sample project)

[codeOfRobin]

Hi!

I have a pretty gnarly crash in my commit editingStyle: forRowAt method that I've managed to reproduce in the Sample App as well.

Steps to reproduce

1. open examples/Kittens, run pod install, run Sample.xcworkspace
2. Try swiping to delete a kitten cell
3. It should crash with an NSInternalInconsistencyException:

 Assertion failure in -[ASTableView _heightForShadowRowAtIndexPath:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3698.16.15/UITableView.m:12202
2019-06-24 03:03:49.317690+0530 Sample[24030:2746589] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView internal inconsistency: missing placeholder context for this index path: <NSIndexPath: 0xc000000000200016> {length = 2, path = 0 - 1}'

This seems to be the exact same issue @fuhailong experienced in #929

[wangwenzhen]

Encountered the same problem without finding the wrong reason