Is ldap_abandon_ext needed after ldap_modify_ext, when return code is not LDAP_SUCCESS?

We are using Mozilla LDAP C SDK 5.12 in our server. We are currently
switching from synchronous calls to asynchronous calls. We would like
to handle all error conditions and do recovery/release actions on error
conditions...etc.

>From the SDK source, it seems like the operations like ldap_modify_ext
may return a positive message ID, even when its return code is not
LDAP_SUCCESS.
In such a scenario:
1. Is it recommended to call ldap_abandon_ext on that message ID to
either free up some allocated resources or for some other reason?
2. Is it unsafe to call ldap_abandon_ext on that message ID as the
return code from ldap_modify_ext is not LDAP_SUCCESS? If it is unsafe,
is it because of the chance in assigning same message ID to some other
request on the same connection handle, which returned LDAP_SUCCESS?

Thanks in advance.