RIS parser handles BT tag incorrect for types other than BOOK

I've changed this to only use BT as primary title for books (not sure where the Unpublished Work type is handled) in ris_parser.inc:

 160             case 'TI':
 161             case 'T1':
 162             case 'CT':
 163               $node_array[$node_id]['title'] = $value;
 164               break;
 165             case 'BT':
 166                 if ( $node_array[$node_id]['biblio_type'] == 100 ) {
 167                     $node_array[$node_id]['title'] = $value; 
 168                 } else {
 169                     $node_array[$node_id]['biblio_secondary_title'] = $value;
 170                 }
 171                 break;