### 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
for (int i = editor_data.get_edited_scene() + 1; i < editor_data.get_edited_scene_count(); i++) {
				tabs_to_close.push_back(editor_data.get_scene_path(i));
			}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_CLOSE_ALL: {
			tab_closing_menu_option = -1;
			for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
				tabs_to_close.push_back(editor_data.get_scene_path(i));
			}
			_proceed_closing_scene_tabs();
		} break;
		case FILE_CLOSE: {
			_scene_tab_closed(editor_data.get_edited_scene());
		} break;
		case SCENE_TAB_CLOSE:
		case FILE_SAVE_SCENE: {
			int scene_idx = (p_option == FILE_SAVE_SCENE) ? -1 : tab_closing_idx;
			Node *scene = editor_data.get_edited_scene_root(scene_idx);
			if (scene && !scene->get_scene_file_path().is_empty()) {
				if (DirAccess::exists(scene->get_scene_file_path().get_base_dir())) {
					if (scene_idx != editor_data.get_edited_scene()) {
						_save_scene_with_preview(scene->get_scene_file_path(), scene_idx);
					} else {
						_save_scene_with_preview(scene->get_scene_file_path());
					}
					if (scene_idx != -1) {
						_discard_changes();
					}
					save_editor_layout_delayed();