Bug 13164: Incorrect ISSN visualization on the normal view if invalid/cancelled ISSN...

Bug 13164: Incorrect ISSN visualization on the normal view if invalid/cancelled ISSN present

Currently, 022$z (and 011$z for UNIMARC) occurences are not shown, but the XSLT
logic used introduces punctuation characters for those $z occurences.

This patch adds a check for the existence of subfield a, and only loops
on $a subfields.

To test:
- Create/have a record with 022$z (or 011$z on UNIMARC) but no 022$a (no 011$a on UNIMARC).
- Open the detail page for the record (on both OPAC and staff).
=> FAIL: the ISSN label and ';' and '.' characters incorrectly shown.
- Repeat mixing with 022$a occurences to notice the bug.
- Apply the patch, reload
=> SUCCES: ISSN label shows only on the presence of a $a, and $z are skipped.
           no matter how many ISSN fields you add.
- Sign off :-D

Regards
To+

Signed-off-by: Frederic Demians <f.demians@tamil.fr>
Works as described on an UNIMARC DB. Mimics what's done for ISBN field.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>