fix "no subtree recompute" when move to root bug introduced in previous commit
fix "no subtree recompute" when move to root bug
introduced in previous commit

clyfe/acts_as_nested_interval,grzlus/acts_as_nested_interval,clyfe/acts_as_nested_interval,grzlus/acts_as_nested_interval,grzlus/acts_as_nested_interval