Fix for requests that doesn't contain an HTTP_USER_AGENT
Fix for requests that doesn't contain an HTTP_USER_AGENT

Some APIs like Paypal IPN send back POST requests to your application which doesn't contain an HTTP_USER_AGENT, causing this gem to crash. This little fix avoids this issue.

mojovski/rack-iframe,merchii/rack-iframe,peburrows/rack-iframe,grimen/rack-iframe