qapi-event: Drop qmp_output_get_qobject() null check

qmp_output_get_qobject() was changed never to return null some time
ago (in commit 6c2f9a15), but the qapi_event_send_FOO() functions
still check.  Clean that up:

|@@ -28,7 +28,6 @@ void qapi_event_send_acpi_device_ost(ACP
|     QMPEventFuncEmit emit;
|     QmpOutputVisitor *qov;
|     Visitor *v;
|-    QObject *obj;
|
|     emit = qmp_event_get_func_emit();
|     if (!emit) {
|@@ -54,10 +53,7 @@ out_obj:
|         goto out;
|     }
|
|-    obj = qmp_output_get_qobject(qov);
|-    g_assert(obj);
|-
|-    qdict_put_obj(qmp, "data", obj);
|+    qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
|     emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err);
|
| out:

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1458254921-17042-7-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
