### 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
if (!bool(EDITOR_GET("interface/scene_tabs/show_thumbnail_on_hover"))) {
		return;
	}
	int current_tab = scene_tabs->get_current_tab();
	if (p_tab == current_tab || p_tab < 0) {
		tab_preview_panel->hide();
	} else {
		String path = editor_data.get_scene_path(p_tab);
		if (!path.is_empty()) {
			EditorResourcePreview::get_singleton()->queue_resource_preview(path, this, "_thumbnail_done", p_tab);
		}
	}
}
void EditorNode::_scene_tab_exit() {
	tab_preview_panel->hide();
}
void EditorNode::_scene_tab_input(const Ref<InputEvent> &p_input) {