Weavers get stuck

Weavers try to fit through gaps they're too big for. A few times now I've given them a build order and a couple of minutes later checked on them to find that they're just endlessly trying to walk through a solar collector.

This may affect other new spider models too, I don't know.

I think it was this battle where it happened last http://zero-k.info/Battles/Detail/31452, towards the end. I spammed BUGS label onto them a few times.