Bug 24424: Advanced editor - interface hangs as "Loading" when given an invalid bib...

Bug 24424: Advanced editor - interface hangs as "Loading" when given an invalid bib number

The Advanced Editor hangs with "Loading, please wait" message when given an
invalid bib number, e.g. /cgi-bin/koha/cataloguing/editor.pl#catalog/55555

This is because in the bug 16424, when changes had been made to
koha-tmpl/intranet-tmpl/lib/koha/cateditor/koha-backend.js
(Bug 16424: Add framework support to advanced MARC editor),
the .fail callback method of the outer .get (in the KohaBackend.GetRecord
function called from cateditor-ui.inc) had been (perhaps by mistake?) removed.
So, in case of failure, the situation is not handled properly.

The proposal is to restore the outer .fail.  As a result, the
openRecord( 'new/', editor, finishCb ); will be called (a standard way
of resolving failed openRecord action (cf. the bottom of cateditor-ui.inc).

Test plan:
==========
0. Be sure your browser does not cache JavaScript for this test.
1. Enable EnableAdvancedCatalogingEditor in the system preferences.
2. Try to open in the advanced editor an unexisting record, e.g.
   http://your_ktd:8081/cgi-bin/koha/cataloguing/editor.pl#catalog/55555
   Koha should hang with a message "Loading, please wait".
3. Apply the patch, restart_all.
4. In a new browser window, repeat p. 2 (remember not to cache JS).
5. The editor should open with a new empty record.

Sponsored-by: Ignatianum University in Cracow
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>