POST CODE!
Please learn how to take screen snapshots without using a camera (WindowsKey-PrintScr).
Connect the panel to outputs earlier in your code. In this case, I’m guessing that one or more of the planes don’t intersect one or both of the curves, so points being passed to Line are null.
Examine the output of every component in your code and understand it before connecting more components downstream.
And please don’t start multiple threads on the same subject. Context and all previous advice is lost that way.