[nftables] bug: rejects single-element intervals as supposedly empty

[Florian Zumbiehl <florz@xxxxxxxx>]

Hi,

I stumbled upon this bug in the Debian buster backports version of nftables
(0.9.2-1~bpo10+1), the git commit log doesn't look like this has been fixed
since, so here it is:

| # nft add rule foo bar udp dport 1-1
| Error: Range has zero or negative size
| add rule foo bar udp dport 1-1
|                            ^^^

Regards, Florian