Bug 11242: fix opac-MARCdetail.pl display and warnings

Bug 11242: fix opac-MARCdetail.pl display and warnings

This patch improves the public catalog MARC view display
of records that contain subfields that are not defined in
the framework used by the bib record.

To test:

(RM note: it may be easier to find or create a MARC record that
 contains a subfield not present in the default framework, then
 load it, rather than fiddle with the MARC frameworks in your
 test database.)

BACK UP YOUR DATABASE!
 1) Search for an item in OPAC
 2) Open OPAC detail
 3) Click 'MARC View' link
 4) Look for something with multiple lines (e.g. 260 or 942)
 5) In another tab, Go to staff client and log in
 6) Go to the staff client URL similar to:
     /cgi-bin/koha/catalogue/detail.pl?biblionumber=##### page
    where ##### is the biblionumber.
 7) Edit -> record
 8) Note the framework used.
 9) More -> Administration
10) MARC bibliographic frameworks
11) Click 'MARC structure' for the framework used by the item
     shown in OPAC.
12) Find the tag (e.g. 260 or 942) and click 'Subfields'
13) Delete of the matching subfields (e.g. 260$b) shown in the
     OPAC tab
14) Clear your opac error log.
15) Refresh OPAC tab. The tag subfields are split.
16) There are opac-MARCdetail.pl warnings.
17) Apply patch
18) Clear your opac error log.
19) Refresh OPAC tab. The tag subfields are no longer split strangely.
20) There are no opac-MARCdetail.pl warnings.
RESTORE YOUR DATABASE.

This also silences a series of warnings triggered by catching
undef hash references.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 38503e18a38116646c9746b13f013b3c11fe55c1)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>