Hi,

I'm getting some CRITICAL logs when accessing the content of the $mbu pseudovariable in a "onsend_route" function. The log lines look like this:

```
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:893 FIXME: null send_sock
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:1479 FIXME: null bind_address
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:493 null send socket
CRITICAL core    35847:core/msg_translator.c:493 null send socket
```

I've checked the msg_translator.c source file and there are many of `LM_CRIT("FIXME: {message}\n");` calls, and I wonder if the "FIXME" tag relates to the location of the error: a Kamailio error or there is an issue in the user code.

Could I have more information about the "FIXME" tag?

Thanks in advance!