Fix JS error when there are categories without any grade items in that category
Fix JS error when there are categories without any grade items in that category

steveswinsburg/gradebookNG,kwedoff1/sakai,duke-compsci290-spring2016/sakai,Fudan-University/sakai,pushyamig/sakai,pushyamig/sakai,zqian/sakai,clhedrick/sakai,rodriguezdevera/sakai,liubo404/sakai,Fudan-University/sakai,ouit0408/sakai,clhedrick/sakai,joserabal/sakai,clhedrick/sakai,colczr/sakai,conder/sakai,pushyamig/sakai,ouit0408/sakai,rodriguezdevera/sakai,ktakacs/sakai,ouit0408/sakai,liubo404/sakai,willkara/sakai,rodriguezdevera/sakai,lorenamgUMU/sakai,bzhouduke123/sakai,joserabal/sakai,willkara/sakai,joserabal/sakai,conder/sakai,colczr/sakai,buckett/sakai-gitflow,bzhouduke123/sakai,frasese/sakai,duke-compsci290-spring2016/sakai,ktakacs/sakai,ktakacs/sakai,zqian/sakai,buckett/sakai-gitflow,conder/sakai,OpenCollabZA/sakai,pushyamig/sakai,bzhouduke123/sakai,rodriguezdevera/sakai,Fudan-University/sakai,ouit0408/sakai,lorenamgUMU/sakai,zqian/sakai,willkara/sakai,colczr/sakai,rodriguezdevera/sakai,OpenCollabZA/sakai,zqian/sakai,Fudan-University/sakai,clhedrick/sakai,clhedrick/sakai,kwedoff1/sakai,OpenCollabZA/sakai,liubo404/sakai,frasese/sakai,zqian/sakai,ktakacs/sakai,willkara/sakai,frasese/sakai,steveswinsburg/gradebookNG,duke-compsci290-spring2016/sakai,OpenCollabZA/sakai,ouit0408/sakai,rodriguezdevera/sakai,pushyamig/sakai,Fudan-University/sakai,frasese/sakai,kwedoff1/sakai,conder/sakai,buckett/sakai-gitflow,ouit0408/sakai,pushyamig/sakai,duke-compsci290-spring2016/sakai,Fudan-University/sakai,buckett/sakai-gitflow,OpenCollabZA/sakai,bzhouduke123/sakai,frasese/sakai,frasese/sakai,ktakacs/sakai,colczr/sakai,duke-compsci290-spring2016/sakai,clhedrick/sakai,clhedrick/sakai,OpenCollabZA/sakai,colczr/sakai,willkara/sakai,pushyamig/sakai,conder/sakai,Fudan-University/sakai,liubo404/sakai,kwedoff1/sakai,joserabal/sakai,bzhouduke123/sakai,liubo404/sakai,buckett/sakai-gitflow,zqian/sakai,willkara/sakai,steveswinsburg/gradebookNG,liubo404/sakai,buckett/sakai-gitflow,colczr/sakai,zqian/sakai,liubo404/sakai,conder/sakai,colczr/sakai,duke-compsci290-spring2016/sakai,kwedoff1/sakai,frasese/sakai,colczr/sakai,bzhouduke123/sakai,OpenCollabZA/sakai,duke-compsci290-spring2016/sakai,lorenamgUMU/sakai,lorenamgUMU/sakai,joserabal/sakai,conder/sakai,joserabal/sakai,buckett/sakai-gitflow,joserabal/sakai,bzhouduke123/sakai,frasese/sakai,Fudan-University/sakai,kwedoff1/sakai,ktakacs/sakai,willkara/sakai,ktakacs/sakai,willkara/sakai,clhedrick/sakai,rodriguezdevera/sakai,rodriguezdevera/sakai,kwedoff1/sakai,buckett/sakai-gitflow,ktakacs/sakai,ouit0408/sakai,lorenamgUMU/sakai,duke-compsci290-spring2016/sakai,joserabal/sakai,lorenamgUMU/sakai,OpenCollabZA/sakai,lorenamgUMU/sakai,conder/sakai,kwedoff1/sakai,ouit0408/sakai,zqian/sakai,lorenamgUMU/sakai,bzhouduke123/sakai,liubo404/sakai,pushyamig/sakai