Sprint burn down is messed up for the closed sprints, burn down is fine for the current sprint.
Reason: I have migrated the workflow for user stories, due to the migration the Sprint value drop down for the user stories is updated to None for the previous sprints.
The burn down is messed up for the previous sprints.
The story points for the user stories is intact for the previous sprints, All i need is to edit the sprint value for the previous sprints user stories to their actual sprint numbers but i am unable to edit the sprint value.