Fix logic error if a port exists in only one port location

If a port is present in /usr/ports/mystuff but not yet in the
ports tree we have to push a version to the versions array to
get the correct index of the existing port location afterwards.

autoupdate.pl

@@ -534,7 +534,7 @@ sub find_newer_ports_dir {
 	foreach my $dir (@port_locations) {
 		my $port_dir = "$dir/$port";
 		my $version = get_ports_version($port_dir);
-		push @versions, $version if $version;
+		push @versions, $version;
 	}
 
 	my $highest