Fix #4273 ignore degenerate triangles in mesher output

src/ifcgeom/kernels/opencascade/OpenCascadeConversionResult.cpp

@@ -129,6 +129,11 @@ void ifcopenshell::geometry::OpenCascadeShape::Triangulate(ifcopenshell::geometr
 					triangles(i).Get(n3, n2, n1);
 				else triangles(i).Get(n1, n2, n3);
 
+				if (dict[n1] == dict[n2] || dict[n2] == dict[n3] || dict[n3] == dict[n1]) {
+					Logger::Warning("Mesher generated a degenerate triangle, ignoring");
+					continue;
+				}
+
 				/* An alternative would be to calculate normals based
 				* on the coordinates of the mesh vertices */
 				/*