Bug 12174 follow-up of the patch (a missing print statement)

http://bugs.koha-community.org/show_bug.cgi?id=12174
Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

opac/opac-export.pl

@@ -102,4 +102,5 @@ else {
             -charset=>'utf-8',
             -attachment=>"bib-$biblionumber.$format");
     }
+    print $marc;
 }