Comment 11 for bug 707290

- Render the gear with an as-large-as-possible center hole?
 - Render an error message as text?

I would be inclined to do both of the above. Apply a clamp to the illegal parameter to force it to stay in the allowed range and avoid the crash. And at the same time use inkex.errormsg() to let the user know what you have done. If I remember correctly, the error message will just be a popup message that will not interfere with the rendering.