qom: don't require user creatable objects to be registered

When an object is in turn owned by another user object, it is not
desirable to expose this in the QOM object hierarchy. It is just an
internal implementation detail, we should be free to change without
exposure to apps managing QEMU.
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

qom/object.c

@@ -646,16 +646,20 @@ Object *object_new_with_propv(const char *typename,
         goto error;
     }
 
-    object_property_add_child(parent, id, obj, &local_err);
-    if (local_err) {
-        goto error;
+    if (id != NULL) {
+        object_property_add_child(parent, id, obj, &local_err);
+        if (local_err) {
+            goto error;
+        }
     }
 
     uc = (UserCreatable *)object_dynamic_cast(obj, TYPE_USER_CREATABLE);
     if (uc) {
         user_creatable_complete(uc, &local_err);
         if (local_err) {
-            object_unparent(obj);
+            if (id != NULL) {
+                object_unparent(obj);
+            }
             goto error;
         }
     }

qom/object_interfaces.c

@@ -75,16 +75,20 @@ Object *user_creatable_add_type(const char *type, const char *id,
         goto out;
     }
 
-    object_property_add_child(object_get_objects_root(),
-                              id, obj, &local_err);
-    if (local_err) {
-        goto out;
+    if (id != NULL) {
+        object_property_add_child(object_get_objects_root(),
+                                  id, obj, &local_err);
+        if (local_err) {
+            goto out;
+        }
     }
 
     user_creatable_complete(USER_CREATABLE(obj), &local_err);
     if (local_err) {
-        object_property_del(object_get_objects_root(),
-                            id, &error_abort);
+        if (id != NULL) {
+            object_property_del(object_get_objects_root(),
+                                id, &error_abort);
+        }
         goto out;
     }
 out: