[Users] GetComponents doesn't handle repository declarations without thorns

[Eric Seidel]

> # Private thorns
> !TARGET   = $ARR
> !TYPE     = ignore
> !CHECKOUT = 
> 
> Note that the checkout item is empty.  GetComponents reports two errors:
> 
> $ utils/Scripts/GetComponents --update --root=. manifest/einsteintoolkit.th 
> Odd number of elements in hash assignment at utils/Scripts/GetComponents line 335.
> Use of uninitialized value in split at utils/Scripts/GetComponents line 441.
> 
> It should instead either report an error, or handle the case of a repository without thorns correctly.

You are right there should be better error tracking here. I think it should probably report the error and exit, there's no reason to have a section with an empty checkout.

Eric