Merge pull request benoitc#2773 from hazho/master

Solving issue benoitc#2692

Author: benoitc

gunicorn/http/wsgi.py

@@ -371,8 +371,8 @@ def sendfile(self, respiter):
  if self.is_chunked():
  chunk_size = "%X\r\n" % nbytes
  self.sock.sendall(chunk_size.encode('utf-8'))
-
- self.sock.sendfile(respiter.filelike, count=nbytes)
+ if nbytes > 0:
+  self.sock.sendfile(respiter.filelike, count=nbytes)
 
  if self.is_chunked():
  self.sock.sendall(b"\r\n")