don't try to decode tag without data

diff --git a/lib/RFID/Serial/Decode/RFID501.pm b/lib/RFID/Serial/Decode/RFID501.pm
index 38b821e..c0176f6 100644 (file)
--- a/lib/RFID/Serial/Decode/RFID501.pm
+++ b/lib/RFID/Serial/Decode/RFID501.pm
@@ -42,6 +42,8 @@ my $item_type = {
 sub to_hash {
        my ( $self, $data ) = @_;
 
+       return unless $data;
+
        my ( $u1, $set_item, $u2, $type, $content, $br_lib, $custom ) = unpack('C4Z16Nl>',$data);
        my $hash = {
                u1 => $u1,      # FIXME