5.5.4 slate global invalidation not updating hittest grid when collapsing parent widget in a retainer widget

[anonymous-edc (Anonymous User)]

Steps to Reproduce
(See repro project)

Widget structure:

1. Retainer box
   1. Modal widget to collapse
      1. Clickable button
   2. Something blocked behind the clickable button

Then make sure slate.enableglobalinvalidation = true and build/cook/run