### 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
edit_theme_item_dialog->set_title(TTR("Add Stylebox Item"));
			break;
		case Theme::DATA_TYPE_MAX:
			break; 
	}
	edit_theme_item_old_vb->hide();
	theme_item_name->clear();
	edit_theme_item_dialog->popup_centered(Size2(380, 110) * EDSCALE);
	theme_item_name->grab_focus();
}
void ThemeItemEditorDialog::_open_rename_theme_item_dialog(Theme::DataType p_data_type, String p_item_name) {
	ERR_FAIL_INDEX_MSG(p_data_type, Theme::DATA_TYPE_MAX, "Theme item data type is out of bounds.");
	item_popup_mode = RENAME_THEME_ITEM;
	edit_item_data_type = p_data_type;
	edit_item_old_name = p_item_name;
	switch (edit_item_data_type) {
		case Theme::DATA_TYPE_COLOR:
			edit_theme_item_dialog->set_title(TTR("Rename Color Item"));
			break;
		case Theme::DATA_TYPE_CONSTANT:
			edit_theme_item_dialog->set_title(TTR("Rename Constant Item"));
			break;
		case Theme::DATA_TYPE_FONT:
			edit_theme_item_dialog->set_title(TTR("Rename Font Item"));
			break;
		case Theme::DATA_TYPE_FONT_SIZE:
			edit_theme_item_dialog->set_title(TTR("Rename Font Size Item"));
			break;
		case Theme::DATA_TYPE_ICON:
			edit_theme_item_dialog->set_title(TTR("Rename Icon Item"));