Unbound - generate keytag query _ta-4f66. NULL IN

[RamSense]

I have been changing my opnsense config to use pihole and all is working.
I rebooted the opnsense and was looking around the logs and configs.
I noticed this in the unbound log:

2021-08-10T21:25:43   unbound[81973]   [81973:0] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T21:25:43   unbound[81973]   [81973:3] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T20:43:11   unbound[81973]   [81973:1] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T19:57:43   unbound[81973]   [81973:0] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T19:45:41   unbound[81973]   [81973:0] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T19:14:20   unbound[81973]   [81973:1] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T18:39:53   unbound[81973]   [81973:0] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T17:42:32   unbound[81973]   [81973:0] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T17:16:22   unbound[81973]   [81973:2] info: generate keytag query _ta-4f66. NULL IN   
2021-08-10T17:16:21   unbound[81973]   [81973:0] info: start of service (unbound 1.13.1).

What is this? Is this a normal thing (I never really looked in the log of unbound)
Or is it something I have done incorrectly or missed? Somebody else experiencing this?
One of the more experienced members will probably know what this Null IN means and if it is a fault of config or an non harmful message.

thank you for your help and explanation in advance!

[RamSense]

still seeing similar mentions: unbound[47709]   [47709:1] info: generate keytag query _ta-4f66. NULL IN

Who can explain what this [generate keytag query _ta-4f66. NULL IN] means?

[bitman]

Seen the same log entries on my OPNsense system;

Some how Unbound stopped (RED) and this is in the log when starting at 2021-09-17T06:18:49 from the Dashboard;

2021-09-17T06:21:47   unbound[56365]   dhcpd entry changed bitmanEV.home.loc @ xxx.xxx.xxx.226.   
2021-09-17T06:21:38   unbound[80917]   [80917:2] info: generate keytag query _ta-4f66. NULL IN   
2021-09-17T06:21:38   unbound[80917]   [80917:1] info: generate keytag query _ta-4f66. NULL IN   
2021-09-17T06:21:38   unbound[80917]   [80917:0] info: start of service (unbound 1.13.2).   
2021-09-17T06:21:38   unbound[80917]   [80917:0] notice: init module 1: iterator   
2021-09-17T06:21:38   unbound[80917]   [80917:0] notice: init module 0: validator   
2021-09-17T06:21:34   unbound[95771]   daemonize unbound dhcpd watcher.   
2021-09-17T06:18:49   unbound[70713]   dhcpd entry changed bitmanEV.home.loc @ xxx.xxx.xxx.227.   
2021-09-17T01:00:15   unbound[50772]   [50772:0] info: 32.000000 64.000000 3   
2021-09-17T01:00:15   unbound[50772]   [50772:0] info: 16.000000 32.000000 14   
2021-09-17T01:00:15   unbound[50772]   [50772:0] info: 8.000000 16.000000 12   
2021-09-17T01:00:15   unbound[50772]   [50772:0] info: 4.000000 8.000000 13   
2021-09-17T01:00:15   unbound[50772]   [50772:0] info: 2.000000 4.000000 18   

[DEC670airp414user]

I started using dns over TLS when this happened:
version of unbound is listed1.19.  and this is the latest business version of opnsense

2023-12-24T04:35:32-05:00   Informational   unbound   [33470:0] info: generate keytag query _ta-4f66. NULL IN   
2023-12-24T04:35:32-05:00   Informational   unbound   [33470:1] info: generate keytag query _ta-4f66. NULL IN   
2023-12-24T03:38:43-05:00   Informational   unbound   [33470:0] info: generate keytag query _ta-4f66. NULL IN   
2023-12-24T00:56:22-05:00   Informational   unbound   [33470:0] info: generate keytag query _ta-4f66. NULL IN   
2023-12-23T21:31:21-05:00   Informational   unbound   [33470:0] info: generate keytag query _ta-4f66. NULL IN   
2023-12-23T20:18:56-05:00   Informational   unbound   [33470:2] info: generate keytag query _ta-4f66. NULL IN   
2023-12-23T20:18:55-05:00   Informational   unbound   [33470:0] info: start of service (unbound 1.19.0).