Curl-matching might be theoretically invalid in 2-RoSy fields #37
Description
When such a field is orthogonal to edge, or near-most so, the dot-products with the edge are almost zero and the matching cannot be deduced. This can only happen in 2-RoSy since in any other (non-degenerate) situation there will always be at least one non-orthogonal vector. Nevertheless, in 2-Rosy principal matching is very likely always the correct choice, since the other direction is a huge rotation. An assertion/warning should be added to curl_matching() in case 2-RoSy is attempted.