### 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
}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_QUIT: {
			project_run_bar->stop_playing();
			_exit_editor(EXIT_SUCCESS);
		} break;
		case RUN_PROJECT_MANAGER: {
			project_run_bar->stop_playing();
			_exit_editor(EXIT_SUCCESS);
			String exec = OS::get_singleton()->get_executable_path();
			List<String> args;
			for (const String &a : Main::get_forwardable_cli_arguments(Main::CLI_SCOPE_TOOL)) {
				args.push_back(a);
			}
			String exec_base_dir = exec.get_base_dir();
			if (!exec_base_dir.is_empty()) {
				args.push_back("--path");
				args.push_back(exec_base_dir);
			}
			args.push_back("--project-manager");
			Error err = OS::get_singleton()->create_instance(args);
			ERR_FAIL_COND(err);
		} break;
		case RELOAD_CURRENT_PROJECT: {
			restart_editor();
		} break;
	}
}
void EditorNode::_update_file_menu_opened() {