dependent value not saved on new nodes when the dependent is inside a fieldset

Problem/Motivation

steps to recreate:

1. create content type and add two fields, one inside a fieldset.
2. create a show / hide dependency, where the field inside the fieldset depends on the value of the outside field.
3. create a new node of the new content type, add value to the dependent, save.
4. go to the edit page, notice the dependent has no value, and if you try again, the value will again be discarded.