### 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
select_all_font_sizes_button = memnew(Button);
	select_full_font_sizes_button = memnew(Button);
	total_selected_font_sizes_label = memnew(Label);
	select_icons_icon = memnew(TextureRect);
	select_icons_label = memnew(Label);
	deselect_all_icons_button = memnew(Button);
	select_all_icons_button = memnew(Button);
	select_full_icons_button = memnew(Button);
	total_selected_icons_label = memnew(Label);
	select_styleboxes_icon = memnew(TextureRect);
	select_styleboxes_label = memnew(Label);
	deselect_all_styleboxes_button = memnew(Button);
	select_all_styleboxes_button = memnew(Button);
	select_full_styleboxes_button = memnew(Button);
	total_selected_styleboxes_label = memnew(Label);
	for (int i = 0; i < Theme::DATA_TYPE_MAX; i++) {
		Theme::DataType dt = (Theme::DataType)i;
		TextureRect *select_items_icon = nullptr;
		Label *select_items_label = nullptr;
		Button *deselect_all_items_button = nullptr;
		Button *select_all_items_button = nullptr;
		Button *select_full_items_button = nullptr;
		Label *total_selected_items_label = nullptr;
		String items_title;
		String select_all_items_tooltip;
		String select_full_items_tooltip;
		String deselect_all_items_tooltip;
		switch (dt) {
			case Theme::DATA_TYPE_COLOR:
				select_items_icon = select_colors_icon;