### 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
_update_title();
	_update_scene_tabs();
	_add_to_recent_scenes(lpath);
	if (editor_folding.has_folding_data(lpath)) {
		editor_folding.load_scene_folding(new_scene, lpath);
	} else if (EDITOR_GET("interface/inspector/auto_unfold_foreign_scenes")) {
		editor_folding.unfold_scene(new_scene);
		editor_folding.save_scene_folding(new_scene, lpath);
	}
	prev_scene->set_disabled(previous_scenes.size() == 0);
	opening_prev = false;
	SceneTreeDock::get_singleton()->set_selected(new_scene);
	EditorDebuggerNode::get_singleton()->update_live_edit_root();
	push_item(new_scene);
	
	if (editor_state_cf->has_section_key("editor_states", "selected_nodes")) {
		TypedArray<NodePath> selected_node_list = editor_state_cf->get_value("editor_states", "selected_nodes", TypedArray<String>());
		for (int i = 0; i < selected_node_list.size(); i++) {
			Node *selected_node = new_scene->get_node_or_null(selected_node_list[i]);
			if (selected_node) {
				editor_selection->add_node(selected_node);
			}
		}
	}
	if (!restoring_scenes) {
		save_editor_layout_delayed();
	}
	return OK;
}
HashMap<StringName, Variant> EditorNode::get_modified_properties_for_node(Node *p_node) {