data_provider_be: fixed dereferencing of 'bad' ptr
In case of failed `dp_req_recv_ptr()` in `be_check_online_done()`
function, `reply` ptr was not initialized and its dereferencing
was a bug.
Resolves: https://pagure.io/SSSD/sssd/issue/3990
Reviewed-by: Tomas Halman <thalman@redhat.com>