Bug 6554: Followup for preferences.pl

Decodes searchfield.

Test plan:
Look for e accent in preferences. You should no longer see converted chars.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Works ok, no errors.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>

admin/preferences.pl

@@ -21,6 +21,7 @@
 use warnings;
 
 use CGI;
+
 use C4::Auth;
 use C4::Context;
 use C4::Koha;
@@ -296,7 +297,8 @@ sub matches {
 my @TABS;
 
 if ( $op eq 'search' ) {
-    my $searchfield = $input->param( 'searchfield' );
+    my $searchfield = $input->param('searchfield');
+    utf8::decode($searchfield);
 
     $searchfield =~ s/\p{IsC}//g;
     $searchfield =~ s/\s+/ /;