[ggevent] Don't die when logging requests
[ggevent] Don't die when logging requests

Some requests, such as websocket requests, may not have headers.

alex/gunicorn,jamesblunt/gunicorn,wong2/gunicorn,zhoucen/gunicorn,zhoucen/gunicorn,zhoucen/gunicorn,ccl0326/gunicorn,gtrdotmcs/gunicorn,elelianghh/gunicorn,jamesblunt/gunicorn,gtrdotmcs/gunicorn,MrKiven/gunicorn,mvaled/gunicorn,1stvamp/gunicorn,1stvamp/gunicorn,ccl0326/gunicorn,prezi/gunicorn,wong2/gunicorn,mvaled/gunicorn,gtrdotmcs/gunicorn,alex/gunicorn,ccl0326/gunicorn,GitHublong/gunicorn,prezi/gunicorn,tejasmanohar/gunicorn,alex/gunicorn,malept/gunicorn,mvaled/gunicorn,z-fork/gunicorn,ephes/gunicorn,malept/gunicorn,harrisonfeng/gunicorn,keakon/gunicorn,wong2/gunicorn,tempbottle/gunicorn,WSDC-NITWarangal/gunicorn,beni55/gunicorn,prezi/gunicorn,jamesblunt/gunicorn,malept/gunicorn,1stvamp/gunicorn,ammaraskar/gunicorn