Bug 36794: Illegitimate modification of biblionumber subfield content (999 $c)

Bug 36794: Illegitimate modification of biblionumber subfield content (999 $c)

It happens that librarians, by mistake, open a biblio editor putting in the
URL, by hand, the biblionumber prefixed with a blank (e.g.
.../addbiblio.pl?biblionumber= 123 -- mind the space before 123).
In such a case the editor opens with the right biblio record (i.e. 123)
but, after saving the record, the content of the biblionumber MARC
field (999 $c for a standard MARC 21 installation) results modified and
contains additional initial blanks.

Moreover, while using ES and making a search for the record (with title,
author etc.) we get two records on the result list (instead of one).

This is because in the addbiblio.pl script $biblionumber is taken (and
continuously used) directly from CGI parameter, without any
validation and/or correction.

Test plan:
==========
0. Have a test installation with ES.
1. Open a biblio record in the editor with an added space before
   biblionumber value, e.g.:
   http://ktd:8081/cgi-bin/koha/cataloguing/addbiblio.pl?biblionumber= 123
   Save the record.
2. From the Normal view choose Save -> MARCXML.  Open the saved file in
   your favourite editor.  You should see, at the end, something like:
   <datafield tag="999" ind1=" " ind2=" ">
     <subfield code="c"> 123</subfield>
   (mind the space before 123).
   This is not right.
3. Make a search with the title or author's name from the record (e.g.
   Henning Mankell for the record 123 from the default ktd data set).
   You should get two records instead of one (while using ES).
4. Apply the patch, restart_all.  Repeat p. 1 and 2 with a different
   biblionumber.  Notice the unchanged (i.e. without spaces) value
   of 999 $c subfield in the exported record and only one record
   as a result of a search.

WNC amended patch - rebased, added conditional in case no bib, moved comments to their own lines

Sponsored-by: Ignatianum University in Cracow
Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit c74169ba27c2e12473239b15358e428bc05da9f5)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 076b82d52036a4779ff762319586dcba24e72cbf)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>