virtual fields that return multiple values need to declare multiple=>1

[drtjmb]

...otherwise for example Xapian indexing fails (lib/cfg.d/search_xapian.pl) - an arrayref gets passed to the TermGenerator when a scalar is expected.

Workaround:

diff --git a/lib/cfg.d/search_xapian.pl b/lib/cfg.d/search_xapian.pl
index b2a923f..2fa6ece 100644
--- a/lib/cfg.d/search_xapian.pl
+++ b/lib/cfg.d/search_xapian.pl
@@ -81,6 +81,7 @@ $c->add_trigger( EP_TRIGGER_INDEX_FIELDS, sub {
                next if $field->isa( "EPrints::MetaField::Langid" );
                next if $field->isa( "EPrints::MetaField::Subobject" );
                next if $field->isa( "EPrints::MetaField::Storable" );
+               next if $field->is_virtual;

                my $prefix = $field->name . ':';
                my $value = $field->get_value( $dataobj );
@@ -97,7 +98,7 @@ $c->add_trigger( EP_TRIGGER_INDEX_FIELDS, sub {
                                $value = $v;
                        }
                        next if !EPrints::Utils::is_set( $value );
-                       $tg->index_text( $value );
+                       $tg->index_text( $value ); # or this will choke on virtual fields that have an arrayref value
                        $tg->increase_termpos();
                        next if length($value) > 200; # Xapian term length limit-ish
                        if( $field->isa( "EPrints::MetaField::Text" ) || $field->isa( "EPrints::MetaField::Name" ) )