run a test again a not well signed (https) website

I'm trying to login again a plesk panel, the url is:

http://ift.tt/1WjkWiQ

the https is not well signed, when the page is loaded appear a warning, and seems that Casperjs go mad with this warning and if you make a photo appear a white screen.

There is any way to jump or fill the warning with casperjs?