Add graceful handling for blank 'Updated Date' from whois.enom.com

Fixes: https://github.com/weppos/whois/issues/320

PRed to official repo as well https://github.com/weppos/whois/pull/321

Applying to our fork so we can patch an issue we are having.

Solution:
allow updated date to be blank for whois.enom.com

Review @byroot @releod