[resolve] "rt" (response time) field not always present when using --severalperprobe
% ./blaeu-resolve -m 11957799 --displayrtt -q A www.nic.mr
[82.151.64.226] : 9 occurrences Average RTT 60 ms
Test #11957799 done at 2018-04-04T13:15:52Z
% ./blaeu-resolve -m 11957799 --severalperprobe -q A --displayrtt www.nic.mr
Traceback (most recent call last):
File "./blaeu-resolve", line 339, in <module>
sets[set_str].rtt += result_i['rt']
KeyError: 'rt'