### Godot version

4.1 rc3

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

This™
![image](https://github.com/godotengine/godot/assets/2223172/cb33110f-a5b0-400a-951f-3fa425f05714)

It can still happen, but it's more difficult to trigger.

### Steps to reproduce

1. Create a new scene with a Control node
2. Add Theme to the Control
3. Open Theme Editor
4. Clear the `theme` property in Control
5. Save, with Theme Editor opened
6. Restart

### Minimal reproduction project

N/A
return;
		}
		Ref<InputEventMouseButton> mb = me;
		if (mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && mb->is_pressed() && dock_popup_selected_idx != nrect) {
			Control *dock = dock_slot[dock_popup_selected_idx]->get_current_tab_control();
			if (dock) {
				dock_slot[dock_popup_selected_idx]->remove_child(dock);
			}
			if (dock_slot[dock_popup_selected_idx]->get_tab_count() == 0) {
				dock_slot[dock_popup_selected_idx]->hide();
			} else {
				dock_slot[dock_popup_selected_idx]->set_current_tab(0);
			}
			dock_slot[nrect]->add_child(dock);
			dock_popup_selected_idx = nrect;
			dock_slot[nrect]->set_current_tab(dock_slot[nrect]->get_tab_count() - 1);
			dock_slot[nrect]->set_tab_title(dock_slot[nrect]->get_tab_count() - 1, TTRGET(dock->get_name()));
			dock_slot[nrect]->show();
			dock_select->queue_redraw();
			_update_dock_containers();
			_edit_current();
			_save_editor_layout();
		}
	}
}
void EditorNode::_dock_popup_exit() {
	dock_select_rect_over_idx = -1;
	dock_select->queue_redraw();
}
void EditorNode::_dock_pre_popup(int p_which) {