Load as Morph with NuScratch's ScratchFrameMorph seems broken

Hi!

This may be something for Tim...

I started with a 5.1 Squeak image and installed NuScratch 382,
created a project and wanted to save it.  That resulted in a DNU
in skinAt:. That seems to work in the latest squeak trunk image.
So I tried to copy my code by saving the ScratchFrame Morph to a
file and load it in the file list with the 'load as morph' button.

However that triggers another error.

I have attached the 5.2 (trunk) error messsage when I read in the
morph as well as the saved morph.

How can I debug this further?

Kind regards

Christian

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