Bug 9016: (follow-up) letter name is not displayed on editing a letter

Bug 9016: (follow-up) letter name is not displayed on editing a letter

On editing a letter, the letter name is not displayed. So if you save
it, the letter name is erased with an empty string.

Signed-off-by: Olli-Antti Kivilahti <olli-antti.kivilahti@jns.fi>
Tested by setting the "Name"-field in letter.pl, saving, re-editing and verifying
that the email is present in the letter's "Name"-field.
The letter "Name" is replicated for each template in the DB, but that doesn't
incur any performance penalty.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>