Applying sampleImage expression via scripting causes AE Beta to freeze (worked previously)

Something in AE Beta has caused a new problem where AE freezes if a script tries to add a sampleImage expression. You can Escape out of the freeze but AE may crash. The expression ends up with a flagged error reported as ‘internal error’ but if you manually click out of the expression field it will apply and work fine. It just freezes if a script applies it.

Steps to reproduce:

1. Import some test QT, drop into a new comp.
2. Apply the Expression Control > Color Control effect
3. Twirl open in timeline and select the Color property
4. Choose File > Script > Run Script File and choose the attached script

AE will freeze. Hit Escape to unfreeze manually. But of course this utterly ruins scripts that use sampleImage to test for things like missing / dropped frames, cut points, etc.