Fix corner-case dialog issue.

Fixed an issue where:

- You are on an Actor Details page.
- You open the "Add Actor Identifier" dialog then close it (so the
  Identifier Types field is populated and in the DOM).
- You open the "Attribute Identifier" dialog which tries to clear all
  the options for "Identifier Type" (which wound up also clearing the
  ones in your "Add Actor Identifier" dialog).
- You open the "Add Actor Identifier" dialog and the Identifier Type
  dropdown was now empty.