[OpenSCAD] bug: edge crossed 'polygons' cause seg fault

[Britton Kerin]

In openscad-2010.01, the following code:

  polygon (points = [[0, 0], [100, 100], [100, 0], [0, 100]],
           paths = [[0, 1, 2, 3]]);

causes a seg fault in root_node->render_csg_term in MainWindow::compile.

Uncross the edges to make a proper polygon and there is no problem:

  polygon (points = [[0, 0], [100, 100], [100, 0], [0, 100]],
           paths = [[0, 2, 1, 3]]);

works fine.

Britton