Bug 17818 - Duplicating a subfield yields an empty subfield tag [follow-up]

Bug 17818 - Duplicating a subfield yields an empty subfield tag [follow-up]

The problem is the same as Bug 17477 but also for dropdown selection list

Steps to reproduce error:
- On the cataloging screen (basic screen), create a new record
- Go to a field with repetable subfields and associated with authorised values
- Select a value for the subfield
 583$x)
 - Clone the subfield
 - select another value for the new subfield
 - Save the record
 - Edit the record to modify => the clone subfield has desappeared.
If you look in DB in marcxml, the subfield is present but without code

 - Apply patch
 - Clean cache browser and reload page
 - Repeat steps above
 - Verify that works as expected

Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>