fix silence_stream size bug

src/mod/formats/mod_tone_stream/mod_tone_stream.c

@@ -96,7 +96,7 @@ static switch_status_t silence_stream_file_read(switch_file_handle_t *handle, vo
 	if (sh->silence) {
 		switch_generate_sln_silence((int16_t *) data, *len, sh->silence);
 	} else {
-		memset(data, 0, *len);
+		memset(data, 0, *len * 2);
 	}
 
 	return SWITCH_STATUS_SUCCESS;