Examine each line of your code. "'Null is null or not an object" usually stems from bad coding. Check that you have all the proper beginning and ending brackets, and all that other stuff that could go wrong when writing code.
Check that you have the latest updates for the application delivering the "'Null is null or not an object" error message. If the coding pertains to a specific application, make sure you have the latest version. Internet Explorer gives this error often, but the new versions are supposed to be better at handling this error.
Visit an online forum that discusses the particular coding and language you are working with and ask them to view your code and point out any errors they may find. A number of things that could be causing the "'Null is null or not an object" error message. But there are lots of generous experts willing to do this, and all you have to do is ask.