fix: yield doesn't return, so needs an else

Author: Tieske

lib/resty/http.lua

@@ -540,8 +540,9 @@ local function _body_reader(sock, content_length, default_chunk_size)
             -- We have a length and potentially keep-alive, but want everything.
             if content_length == 0 then
                 co_yield("")
+            else
+                co_yield(sock:receive(content_length))
             end
-            co_yield(sock:receive(content_length))
 
         else
             -- We have a length and potentially a keep-alive, and wish to stream