> Perspective
Yes. There was actually code in the function for dealing with a possible NULL in the main iPtr->cmdFramePtr already. Given this it was considered to be possible for such a NULL to wind up in the corPtr->caller.cmdFramePtr as well.

> Merging
Ok.

> Test(s)
While accepting the possibility of a NULL winding up in the coro cmdFrame I am not sure yet how it actually happens. So, from me I have no prospects of crafting the necessary test.

And yes, I do wish that Colin had taken the time to reduce his script as much as possible.