Fix missing shapes in compound shapes

[jpumc]

When a compound shape has multiple shapes, some shapes were skipped when a conditional shapes condition is false. This occurred in reduce when a was non-empty and b was empty. The result was that any missing shape removed any shapes before it.

[gigaherz]

I wrote this far too long ago to remember what this did or how it worked so I'll assume what you say is correct. I'm far too deep in trying to add scripting to switch my brain right now. XD