Fixes#11435
Draft_Fillet could already handle arcs, provided they were not Draft_Arcs. The `_extract_edge` function in make_fillet.py had a strange logic, and could also return a wire which would result in problems later.
Another issue was that the `fillet` function in fillets.py did not handle the order of the edges correctly if one of the edges was an arc and the other a straight edge. The arch had to be selected first to prevent this error.
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