### Godot version

v4.2.dev.custom_build [0c2144da9]

### System information

Debian Linux X11 Xfce

### Issue description

Prerequisite: Be in Single Window Mode in the Editor
The Filesystem Dock is unusable when it is floating, which is not expected.
It appears garbled in the top-left corner:
![image](https://github.com/godotengine/godot/assets/6299227/109f7922-97de-44c3-814a-ca7f970e0602)

The following errors are shown:
```
  editor/window_wrapper.cpp:220 - Condition "!is_window_available()" is true.
  editor/window_wrapper.cpp:202 - Condition "!get_window_enabled()" is true. Returning: Rect2i()
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
```

bisecting lead to #62378
possibly related to #44439

### Steps to reproduce

1. Start a project in the Editor
2. Switch to Single Window Mode in the Editor and reload (if necessary)
3. Make the Filesystem Dock floating

### Minimal reproduction project

Editor issue
if (!p_object) {
		InspectorDock::get_inspector_singleton()->edit(nullptr);
		NodeDock::get_singleton()->set_node(nullptr);
		SceneTreeDock::get_singleton()->set_selected(nullptr);
		InspectorDock::get_singleton()->update(nullptr);
		hide_unused_editors();
		return;
	}
	ObjectID id = p_object->get_instance_id();
	if (id != editor_history.get_current()) {
		if (p_inspector_only) {
			editor_history.add_object(id, String(), true);
		} else if (p_property.is_empty()) {
			editor_history.add_object(id);
		} else {
			editor_history.add_object(id, p_property);
		}
	}
	_edit_current();
}
void EditorNode::save_default_environment() {
	Ref<Environment> fallback = get_tree()->get_root()->get_world_3d()->get_fallback_environment();
	if (fallback.is_valid() && fallback->get_path().is_resource_file()) {
		HashMap<Ref<Resource>, bool> processed;
		_find_and_save_edited_subresources(fallback.ptr(), processed, 0);
		save_resource_in_path(fallback, fallback->get_path());
	}
}
void EditorNode::hide_unused_editors(const Object *p_editing_owner) {