fix warnings

when draining output from rfid reader

diff --git a/lib/RFID/Biblio/Reader/3M810.pm b/lib/RFID/Biblio/Reader/3M810.pm
index b3848c4..a0d127c 100644 (file)
--- a/lib/RFID/Biblio/Reader/3M810.pm
+++ b/lib/RFID/Biblio/Reader/3M810.pm
@@ -56,8 +56,10 @@ sub init {
 
        # drain on startup
        my ( $count, $str ) = $port->read(3);
-       my $data = $port->read( ord(substr($str,2,1)) );
-       warn "drain ",as_hex( $str, $data ),"\n";
+       if ( $count ) {
+               my $data = $port->read( ord(substr($str,2,1)) );
+               warn "drain ",as_hex( $str, $data ),"\n";
+       }
 
        $port->read_char_time(100);      # 0.1 s char timeout
        $port->read_const_time(500); # 0.5 s read timeout