### Godot version

v4.0.beta.custom_build [eaf306e0b]

### System information

Windows 10

### Issue description

Selecting a `Window` node in the Editor's SceneTree results in the message
```
editor/editor_data.cpp:1058 - Parameter "p_node" is null.
```
and the Inspector shows empty content instead of the Window's properties.

I would expect, that clicking on a node in the SceneTree lets me edit the properties of the node.

Bisecting shows that this behavior got introduced in #71770

### Steps to reproduce

1. Create a Window node
2. Click on the Window node in the Editor's SceneTree

### Minimal reproduction project

N/A
if (p_visible) {
		button->show();
		EditorNode::get_singleton()->make_bottom_panel_item_visible(theme_editor);
	} else {
		if (theme_editor->is_visible_in_tree()) {
			EditorNode::get_singleton()->hide_bottom_panel();
		}
		button->hide();
	}
}
ThemeEditorPlugin::ThemeEditorPlugin() {
	theme_editor = memnew(ThemeEditor);
	theme_editor->set_custom_minimum_size(Size2(0, 200) * EDSCALE);
	button = EditorNode::get_singleton()->add_bottom_panel_item(TTR("Theme"), theme_editor);
	button->hide();
}