Bug: Editing database credentials duplicates data

If you edit a Select Box and re-enter the database credentials, you get duplicate records.
0. Set up a MySQL database with several rows of alpha data.
1. Create a new form.
2. Add a new field of type Select Box.
3. Click _Select options from database_
4. Enter valid credentials for the database
5. Select a table and a column. Order by alpha asc.
6. Click Save
7. Click Apply and then Save
8. On a new page, enter the form ID shortcode.
9. View the page.
–> data is OK
10. Go back to the editor and edit the Select Box field.
11. Click _Select options from database_
12. Enter the same credentials and table & column choices as above.
13. Save, Apply, Save
14. Refresh the page containing the form.
Actual result: the data is duplicated (repeated at the end). Every time you re-enter the credentials, you get another duplicate set of the same data.
Expected result: Re-entering the database credentials and parameters should generate only one copy of the data.

Workaround: Delete the field and set it up again.