Bug 30746: Fix JS error on opac-memberentry

Bug 30746: Fix JS error on opac-memberentry

Empty PatronSelfRegistrationBorrowerMandatoryField and PatronSelfRegistrationBorrowerUnwantedField
Go to opac-memberentry.pl
Notice the JS error
  Uncaught TypeError: j is undefined
Apply this patch
Go to opac-memberentry.pl
=> no JS error
Fill the pref with some values
Go to opac-memberentry.pl
=> Confirm that the fields you marked as mandatory as flagged accordinly
on the UI

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>