rdata of "." causes "dnsdbq: sort.c:254: sortable_dnsname: Assertion `new_size != 0' failed."

[djw1149]

An rdata value of just "." causes a dnsdbq that is sorting json input to fail.

$ echo '{"count":77,"time_first":1577896176,"time_last":1585560550,"rrname":"9ctrl.com.cn.","rrtype":"NS","rdata":"."}'  | dnsdbq -J - -j -s
dnsdbq: sort.c:254: sortable_dnsname: Assertion `new_size != 0' failed.
Aborted

Function countoff() returns 0 for "." and function sortable_dnsname() asserts a failure for that.

Another way to get that data: dnsdbq -j -l 0 -r "9ctrl.com.cn." -s -k first