Contour node error

If you do not have a connection from the video output of contour node it breaks and does not send x, y, contour x, y outputs. Any idea why?
See attached node but it is the same with the one at the help file.

contour error.v4p (14.4 kB)

that is not an error but that is how it works. the contour node only runs if something is connected downstream its video output.