Simple avoidable NPE; patch pending. To replicate:
1.) Create a course site w/ GB2 included; weight by categories.
2.) Create a single category, name it anything you want, do not let it be extra credit.
3.) Create a grade item, name it anything, leave at defaults.
4.) Duplicate course site.
5.) Go into the duplicate site and try to change the graded item to be included in the grade.
6.) You'll receive a 500 error on clicking Save; a bug report will be generated with a stacktrace pointing to the problem code line.