update-shape throws a Lisp exception when run on a sprite box that has been changed into a doit box

[rigdern]

This issue raises the question: should the "Flip to Doit" command be allowed on sprite & graphics boxes?

Repro steps

I reproed this on Boxer 3.4.19 2024-06-24

1. Make a new graphics box (Make > Graphics menu item)
2. Name the sprite sprite
3. Change sprite to a doit box (Box > Flip to Doit)
4. Change the code in sprite.SHAPE to stamp-circle 20
5. Outside of the graphics box, run the line tell sprite update-shape

Unexpected result: A Common Lisp exception is thrown:

Lisp Error:#(BOXER::INVALID-VALUE-BOX-INTERFACE (0.0 0.0) #<DATA-BOX 0.00 0... > #<DOIT-BOX Show-S... > BOXER::HOME-POSITION) fell through ETYPECASE expression inside BOXER:VIRTUAL-COPY.
Wanted one of (BOXER:VIRTUAL-COPY BOXER::VIRTUAL-PORT BOXER::BOX NUMBER SYMBOL BOXER::FOREIGN-DATA). 

The issue can also be reproed with update-shape repro.box.zip.

Potential fixes

I see two options for fixing the issue:

1. Prevent sprite boxes from being flipped into doit boxes
2. Or ensure an exception isn't thrown in running update-shape on a sprite box that is a doit box

# Should the "Flip to Doit" command be allowed on sprite & graphics boxes?

Sometimes when trying to click into a sprite or graphics box, I accidentally turn it into a doit box. This also happens sometimes when I hit the wrong keyboard shortcut. When this happens, the change is subtle: the corners of the box change from round to square. The box's label remains unchanged as "Graphics" or "Sprite". I often don't notice until later that the sprite/graphics box has become a doit box.

So I think (1) could improve the user experience.