(url-http-parse-headers): Reset url-http-data to nil,

like for the 303 response.

lisp/url/url-http.el

@@ -459,7 +459,7 @@ should be shown to the user."
 	      (url-http-debug "Converting `%s' request to `GET' because of REDIRECT(%d)"
 			      url-http-method url-http-response-status)
 	      (setq url-http-method "GET"
-		    url-request-data nil)))
+		    url-http-data nil)))
 	   (303
 	    ;; The response to the request can be found under a different
 	    ;; URI and SHOULD be retrieved using a GET method on that