steipete/AFDownloadRequestOperation — pull request #60 by kyungkoo (2014-02-06 02:24:18+00:00)
Title: move self.progressiveDownloadProgress check to dispatch_async block

Before execute dispatch_async block, we checked self.progressiveDownloadProgress is nil.
But, although this object is not nil, inside dispatch_async block, this object can not be guaranteed nil or not.
So I changed nil check inside of dispatch_async block.