Fix for crash bug caused by Iframe NULL reference
Fix for crash bug caused by Iframe NULL reference

https://github.com/ariya/phantomjs/issues/10947
https://github.com/ariya/phantomjs/issues/11103
https://github.com/ariya/phantomjs/pull/11984

DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs,DocuSignDev/phantomjs