Object not selected in hierarchy gives an error

Hi, I have a problem with my project. I have an object with script attached to it. If I don't select this object in the hierarchy with the mouse and run the project, it gives me an error NullReferenceException. But if I selected the object and do run, the error doesn't appear anymore. Any ideas why it happens like that?

Thanks.

PostEdit: I found the answer to the problem. I was missing a line of code "myarray[i] = new Array();", which led to this behavior.