Strange message appearing in logs from isc-dhcpd-V3.1.0

[Niall O'Reilly]

	One of our soon-to-be retired servers is running isc-dhcpd-V3.1.0.

	A few days ago, after a routine re-start, it began to log the following
	message, which I don't recall ever seeing before.

dhcp.c(3956): non-null pointer

	The message seems to be generated for each request/response pair: 
	DISCOVER/OFFER, REQUEST/ACK, and INFORM/ACK.

	AFAICS, things are otherwise normal: the lease file is growing; clients
	involved are going quiet after ACK rather than trying again to obtain a
	response.

	I don't understand the code at dhcp.c(3956) enough to see what might be
	going on.

	I'ld appreciate hints as to whether I need to be alarmed and/or what
	I need to do.

	Best regards,
	Niall O'Reilly