Bug 37755: Fixed JavaScript for modification tabs

Bug 37755: Fixed JavaScript for modification tabs

This patch addresses a new bug which prevents correct submission on mod
borrowers and mod records (mod + delete). The bug appears to have been
introduced since the recent Bootstrap5 switch, and shouldn't be surfacing
anywhere else in the system

Note that the test plan focuses on tools/modborrowers.pl. The error also
appears to exist on tools/batch_record_modification.pl and
tools/batch_delete_records.pl, but is a lot harder to reproduce.

Please see https://chat.koha-community.org/koha-community/pl/fmnzzgy5cpghtpdc9a9ow75scr
and follow-up comments for details on reproducing this.

To test:
a)  go to tools/modborrowers.pl and try to enter valid cardnumbers or
    borrowernumbers
    1)  notice how you cannot proceed
b)  APPLY PATCH
c)  repeat steps a
    1)  notice how you can now proceed
d)  SIGN OFF

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>