Can't remove a dependency once added

Steps to reproduce:

1. Create 2 tasks with the same project
2. Edit one of them
3. Mark the other task as a dependency
4. Click Save & View
5. Observe the "Dependencies" section added
6. Edit the task again
7. Remove the tick box (to remove a dependency)
8. Click on Save & View

Expected results: The dependency is removed once the tick box is cleared.

Actual results: The dependency still remains.