Date picker does not display in modal

Overview:

Date picker does not display when the control is in a modal.

Example:

1. Create new Agreement
2. Click "Add license" button in New agreement form
3. Click "Link license"
4. In modal search/sort, scroll to "Start date" in filter list, open, and click date picker icon

Expected Results:

Date picker shown
Actual Results:

Nothing happens
Additional Information:
Affects date pickers in other modals (e.g. ui-plugin-find-po-line)
Interested parties:

adityamatukumalli
dennisbridges