fix negative stats

[dogancanbakir]

Closes #1366

$ go run . -d domain.com -all -stats

               __    _____           __         
   _______  __/ /_  / __(_)___  ____/ /__  _____
  / ___/ / / / __ \/ /_/ / __ \/ __  / _ \/ ___/
 (__  ) /_/ / /_/ / __/ / / / / /_/ /  __/ /    
/____/\__,_/_.___/_/ /_/_/ /_/\__,_/\___/_/

                projectdiscovery.io

[INF] Current subfinder version v2.6.6 (latest)
[INF] Loading provider config from /Users/dogancanbakir/Library/Application Support/subfinder/provider-config.yaml
[INF] Enumerating subdomains for domain.com

neda.domain.com
newdv.default.domain.com
www.admin.domain.com
...
[INF] Found 5606 subdomains for domain.com in 30 seconds 53 milliseconds
[INF] Printing source statistics for domain.com

 Source               Duration      Results     Errors
────────────────────────────────────────────────────────
 alienvault           29.137s            21          0
 anubis               233ms            3887          0
 builtwith            0s                  0          0
 chaos                1.205s              0          1
 columbus             301ms               8          0
 commoncrawl          9.579s             71          0
 crtsh                4.289s              5          0
 digitorus            444ms               1          0
 dnsdb                0s                  0          0
 dnsdumpster          1.809s              0          0
 fofa                 1.324s              0          1
 github               314ms               0          1
 hackertarget         851ms               5          0
 leakix               343ms               1          0
 netlas               1.431s              0          1
 rapiddns             3.354s             79          0
 securitytrails       2.217s           1352          0
 shodan               226ms             176          0
 sitedossier          4.716s              0          1
 subdomaincenter      221ms               0          1
 virustotal           0s                  0          0
 waybackarchive       30s                 0          1
 zoomeyeapi           1.042s              0          0


 The following sources were included but skipped...

 bevigil
 binaryedge
 bufferover
 c99
 censys
 certspotter
 chinaz
 dnsrepo
 facebook
 fullhunt
 hunter
 intelx
 passivetotal
 quake
 redhuntlabs
 robtex
 threatbook
 whoisxmlapi