### 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
current_menu_option = p_id;
			layout_dialog->set_title(TTR("Save Layout"));
			layout_dialog->set_ok_button_text(TTR("Save"));
			layout_dialog->set_name_line_enabled(true);
			layout_dialog->popup_centered();
		} break;
		case SETTINGS_LAYOUT_DELETE: {
			current_menu_option = p_id;
			layout_dialog->set_title(TTR("Delete Layout"));
			layout_dialog->set_ok_button_text(TTR("Delete"));
			layout_dialog->set_name_line_enabled(false);
			layout_dialog->popup_centered();
		} break;
		case SETTINGS_LAYOUT_DEFAULT: {
			_load_docks_from_config(default_layout, "docks");
			_save_editor_layout();
		} break;
		default: {
			Ref<ConfigFile> config;
			config.instantiate();
			Error err = config->load(EditorSettings::get_singleton()->get_editor_layouts_config());
			if (err != OK) {
				return; 
			}
			_load_docks_from_config(config, editor_layouts->get_item_text(p_id));
			_save_editor_layout();
		}
	}
}
void EditorNode::_scene_tab_script_edited(int p_tab) {