I do not get a crash if I run "page" when a plot window is not active, but I do if I run it when there are no child windows open. I don't think this is necessarily a bug. There are several commands that will crash Origin when run in an empty project. It's just something you have to be aware of when you are writing your scripts.
Mike's advice for script writing is good: you should always check that conditions are correct for your script. Is the active window a graph? Is there a worksheet selection? etc. Nevertheless, this is a bug and should be treated that way. You should be sending bug reports via email to tech@originlab.com. I'll see that this this gets put in our bug database.