Bug 16668: Fix t/Ris.t tests

Caused by bug 16442.
Now we need to mock the marcflavour pref

Test plan:
  prove t/Ris.t
should return green

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

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

C4/Ris.pm

@@ -558,6 +558,7 @@ $clean_subtitle ||= q{};
 	## be written and designated. The field is free-form and resistant
 	## to all parsing efforts, so this information is lost on me
     }
+    return;
 }
 
 ##********************************************************************
@@ -590,6 +591,7 @@ sub print_stitle {
 	    }
 	}
     }
+    return;
 }
 
 ##********************************************************************

t/Ris.t

@@ -3,15 +3,15 @@
 # This Koha test module is a stub!  
 # Add more tests here!!!
 
-use strict;
-use warnings;
+use Modern::Perl;
 
+use t::lib::Mocks;
 use Test::More tests => 4;
 
 BEGIN {
     use_ok('C4::Ris');
 }
-
+t::lib::Mocks::mock_preference('marcflavour', 'MARC21');
 is(C4::Ris::print_typetag(),undef,'test printing typetag');
 
 is(C4::Ris::print_title(),undef, 'test printing title when print_title is nil');