Fix bug in sendfile.rb
Fix bug in sendfile.rb

The error message called `variation` without the env leading to an `ArgumentError`. It should call `type` instead.
wjordan/rack,wildjcrt/rack,tylergannon/rack,rwz/rack,Comcast/rack,gfvcastro/rack,zjsxwc/rack,akihiro17/rack,ngpestelos/rack,arronmabrey/rack,arronmabrey/rack,sigmavirus24/rack,eins78/rack,wildjcrt/rack,keithduncan/rack,Codeman655/rack,evanphx/rack,rwz/rack,keepcosmos/rack,zjsxwc/rack,tylergannon/rack,nmk/rack,arronmabrey/rack,Eric-Guo/rack,akihiro17/rack,chneukirchen/rack,stepri/rack,eavgerinos/rack,ganmacs/rack,davydovanton/rack,gioele/rack,eins78/rack,maclover7/rack,jackxxu/rack,Comcast/rack,wjordan/rack,jeremyf/rack,eavgerinos/rack,AMekss/rack,laplaceliu/rack,trexnix/rack,ganmacs/rack,davidcelis/rack,jackxxu/rack,supzann3/rack,shaneog/rack,gfvcastro/rack,chneukirchen/rack,deepj/rack,evanphx/rack,liamseanbrady/rack,stepri/rack,Codeman655/rack,evanphx/rack,liamseanbrady/rack,trexnix/rack,rwz/rack,fabianrbz/rack,laplaceliu/rack,Eric-Guo/rack,imtayadeway/rack,wildjcrt/rack,gfvcastro/rack,wjordan/rack,laplaceliu/rack,davidcelis/rack,sigmavirus24/rack,supzann3/rack,keepcosmos/rack,Eric-Guo/rack,gioele/rack,akihiro17/rack,AMekss/rack,liamseanbrady/rack,maclover7/rack,stepri/rack,deepj/rack,AMekss/rack,deepj/rack,keithduncan/rack,imtayadeway/rack,sigmavirus24/rack,zjsxwc/rack,eavgerinos/rack,fabianrbz/rack,ngpestelos/rack,davydovanton/rack,nmk/rack,nmk/rack,gioele/rack,davydovanton/rack,ganmacs/rack,shaneog/rack,keithduncan/rack,ngpestelos/rack,Comcast/rack,krainboltgreene/lack,fabianrbz/rack,trexnix/rack,maclover7/rack,eins78/rack,jackxxu/rack,davidcelis/rack,Codeman655/rack,shaneog/rack,imtayadeway/rack,tylergannon/rack,jeremyf/rack,keepcosmos/rack,supzann3/rack,chneukirchen/rack,jeremyf/rack