Bug 20126: (follow-up bug 10455) Restore MARC field length calculation in ModBiblioMarc

Trivial fix. Problem raised by bug 10455.

Test plan:
[1] Create or edit biblio record.
[2] Save and check leader field lengths in MARC view.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

C4/Biblio.pm

@@ -3337,6 +3337,8 @@ sub ModBiblioMarc {
         format       => 'marcxml',
         marcflavour  => C4::Context->preference('marcflavour'),
     };
+    $record->as_usmarc; # Bug 20126/10455 This triggers field length calculation
+
     # FIXME To replace with ->find_or_create?
     if ( my $m_rs = Koha::Biblio::Metadatas->find($metadata) ) {
         $m_rs->metadata( $record->as_xml_record($encoding) );