Bug 17281 Warning when saving subfield structure

Bug 17281 Warning when saving subfield structure

TO TEST:

1. Home > MARC Framework > Default > Actions > MARC structure
2. On 073 field (for example), click Edit
3. Click on Edit subfield button
4. Click on Save changes
5. Take a look in intranet logs. You find:
   Use of uninitialized value in string eq at
   ../admin/marc_subfields_structure.pl
6. Apply the patch, and repeat steps 3-5
   => no more warning in log

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 259679e9dece15b69b216b8e39f8e4ebd0b58800)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>