Bug 23762: Editing is_html status of email template fails under multi-languages

Bug 23762: Editing is_html status of email template fails under multi-languages

To test:
1.Enable multi-languages
2.Set the preference 'TranslateNotices' on  'Allow'
3.Go to: tools==>Notices & slips==>Edit (one notice)
4.Click on the "Email" in the Default, uncheck the checkbox for 'HTML Messages'.
5.Save
6.Reopen the notice, nothing changed.
7.Apply the patch
8.Repeat the steps 4 and 5
9.Success.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>