RGB value of (0,0,0) causes divide by zero error

[WizBangCrash]

Hi Ben,
I am using your RGB Converter in a project I am doing and noticed that if your rgb_to_xy() method is called with an RGB value of (0,0,0), a divide by zero error occurs.
I have made the following change to the method:
if not (red or green or blue):
point = XYPoint(0,0)
else:
point = self.color.get_xy_point_from_rgb(red, green, blue)
return (point.x, point.y)

I thought you'd like to know.
Thanks for the classes they are very useful :-)