Don't scan the filter table for jumps to 'blacklst' if the 'blacklst' chain does not exist

Signed-off-by: Tom Eastep <teastep@shorewall.net>

Shorewall/Perl/Shorewall/Chains.pm

@@ -3684,9 +3684,12 @@ sub expand_rule( $$$$$$$$$$;$ )
 # the associated interface chain
 #
 sub promote_blacklist_rules() {
-    my $promoted = 1;
     my $chainbref = $filter_table->{blacklst};
 
+    return 1 unless $chainbref;
+
+    my $promoted = 1;
+
     while ( $promoted ) {
 	$promoted = 0;