gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed

Apr 24 20:20:17 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:17 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:17 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:17 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:17 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:17 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: clutter_layout_manager_get_child_meta: assertion 'CLUTTER_IS_LAYOUT_MANAGER (manager)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed
Apr 24 20:20:18 debian gnome-shell[2463]: g_object_set: assertion 'G_IS_OBJECT (object)' failed

...[3654] times

Why there are so many failed message is in my syslog (sudo cat /var/log/syslog) file?
When I searched this on the Internet, I found a similar bug report on LaunchPad1.

OS: Debian GNU/Linux 9 (stretch) 64-bit
Kernel: 4.9.144-3.1 (2019-02-19)
Gnome-shell version: GNOME Shell 3.22.3