Fix naming bug

lms/static/coffee/src/staff_grading/staff_grading.coffee

@@ -234,7 +234,7 @@ class StaffGrading
 
   graded_callback: () =>
     @grade = $("input[name='grade-selection']:checked").val()
-    if score == undefined
+    if @grade == undefined
       return
     # check to see whether or not any categories have not been scored
     num_categories = $('table.rubric tr').length