FIJI Settings: ignore undefined net names when looking for duplicate instrumentations

bin/FIJI/Settings.pm

@@ -303,12 +303,16 @@ sub read_settingsfile ($$$) {
             return (undef, $msg);
         }
 
-        if (defined $dup->{$fiu_ref->{'FIU_NET_NAME'}}) {
-            my $msg = "More than one FIU attached to ".$fiu_ref->{'FIU_NET_NAME'};
-            $logger->warn($msg);
-            $warn .= $msg;
-        } else {
-            $dup->{$fiu_ref->{'FIU_NET_NAME'}} = 1;
+        # Test for multiple instrumentations of a single net
+        my $netname = $fiu_ref->{'FIU_NET_NAME'};
+        if (defined($netname) && length($netname) > 0) {
+            if (defined $dup->{$netname}) {
+                my $msg = "More than one FIU attached to $netname";
+                $logger->warn($msg);
+                $warn .= $msg;
+            } else {
+                $dup->{$fiu_ref->{'FIU_NET_NAME'}} = 1;
+            }
         }
 
         $fiji_settings_ref->{'fius'}->[$fiu_num] = $fiu_ref;