### 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
}
	} else {
		sdata->set_path(lpath, true); 
	}
	Node *new_scene = sdata->instantiate(p_set_inherited ? PackedScene::GEN_EDIT_STATE_MAIN_INHERITED : PackedScene::GEN_EDIT_STATE_MAIN);
	if (!new_scene) {
		sdata.unref();
		_dialog_display_load_error(lpath, ERR_FILE_CORRUPT);
		opening_prev = false;
		if (prev != -1) {
			set_current_scene(prev);
			editor_data.remove_scene(idx);
		}
		return ERR_FILE_CORRUPT;
	}
	if (p_set_inherited) {
		Ref<SceneState> state = sdata->get_state();
		state->set_path(lpath);
		new_scene->set_scene_inherited_state(state);
		new_scene->set_scene_file_path(String());
	}
	new_scene->set_scene_instance_state(Ref<SceneState>());
	set_edited_scene(new_scene);
	String config_file_path = EditorPaths::get_singleton()->get_project_settings_dir().path_join(p_scene.get_file() + "-editstate-" + p_scene.md5_text() + ".cfg");
	Ref<ConfigFile> editor_state_cf;
	editor_state_cf.instantiate();
	Error editor_state_cf_err = editor_state_cf->load(config_file_path);
	if (editor_state_cf_err == OK || editor_state_cf->has_section("editor_states")) {
		_load_editor_plugin_states_from_config(editor_state_cf);
	}