 
   # Student's course average
   numTasksStudent = 0
-  numTasksStudent += 1 for studentTask in student.data when studentTask.is_included_in_averages
+  numTasksStudent += 1 for studentTask in student.data when studentTask?.is_included_in_averages
 
   student.average_score =
     ( student.average_score - ( oldScore / numTasksStudent ) ) +

  # Overall course averages
  taskCount = 0
  for student in course.students
    taskCount += 1 for studentTask in student.data when studentTask.is_included_in_averages

  course.overall_average_score =
    (course.overall_average_score - ( oldScore / taskCount ) ) +

  # Assignment averages
  numStudentsTask = 0
  for student in course.students
    for studentTask, i in student.data when studentTask
      if i is columnIndex
        numStudentsTask += 1 if studentTask.is_included_in_averages

