gitweb: Drop the href() params which keys are not in %mapping

If someone would enter parameter name incorrectly, and some key of
%params is not found in %mapping hash, the parameter is now
ignored. Change introduced by Martin Waitz in commit
  756d2f064b
tried to do that, but it left empty value and there was doubled ";;"
in returned string.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -285,7 +285,7 @@ sub href(%) {
 	my $href = "$my_uri?";
 	$href .= esc_param( join(";",
 		map {
-			"$mapping{$_}=$params{$_}" if defined $params{$_}
+			defined $params{$_} ? "$mapping{$_}=$params{$_}" : ()
 		} keys %params
 	) );