While editing saved as draft form: attempt to invoke interface method 'int java.util.list.size()' on a null object reference

Hi @ssraza
Welcome to the ODK forum. We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a picture as your avatar because it helps build community!

What version of ODK Collect are you using?
Is it a problem with just that one form? If so could you share it here?