Instant crash when raw geometry of dwg import is manipulated

[sWilliams]

Reproducable SU crash

Good question, I did some more digging. We have a hard limit on the number of edges in the algorithm that detects new loops. If the algorithm traverses 10,000 connected edges without hitting a repeat, it gives up. I believe that the workaround (create several faces and then merge them) uses another code path.