Bug 23102: 404 errors on page causes SCI user to be logged out

Bug 23102: 404 errors on page causes SCI user to be logged out

To test:
 1 - Have something on the SCO page that won't load
     Add to SCOUserJS:
        </script>
        <img src="http://localhost:8080/silk/famfamfam.png"/>
        <script>
 2 - Enable the SCO and SCI system preferences:
     WebBasedSelfCheck: Enable
     SelfCheckInModuke: Enable
     AutoSelfCheckAllowed: Allow
     AutoSelfCheckID / AutoSelfCheckPass to a valid user with permissions
 3 - Add the self_checkin_module and self_checkout_module permissions to the AutoSelfCheck user
 4 - Access the selfcheckout module https://yoursite.org/cgi-bin/koha/sco/sco-main.pl
 5 - Sign in using a patron
 6 - Enter an unkown barcode, I used "DONTMATTER"
 7 - If not logged out, click to 'Return to account summary'
 8 - You are asked to sign in again
 9 - Repeat with the SCI module
10 - Apply patch
11 - Repeat, but this time you can return to account

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 5bab87f76b05bbf8627cf6786975e9e30a5f2f6c)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>