[http] Avoid closing stdout (Fixes #3686)

youtube_dl/downloader/http.py

@@ -193,6 +193,7 @@ class HttpFD(FileDownloader):
             self.to_stderr(u"\n")
             self.report_error(u'Did not get any data blocks')
             return False
+        if tmpfilename != u'-':
             stream.close()
         self.report_finish(data_len_str, (time.time() - start))
         if data_len is not None and byte_counter != data_len: