### 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
if (err != OK) {
		show_accept(TTR("Couldn't save scene. Likely dependencies (instances or inheritance) couldn't be satisfied."), TTR("OK"));
		return;
	}
	int flg = 0;
	if (EDITOR_GET("filesystem/on_save/compress_binary_resources")) {
		flg |= ResourceSaver::FLAG_COMPRESS;
	}
	flg |= ResourceSaver::FLAG_REPLACE_SUBRESOURCE_PATHS;
	err = ResourceSaver::save(sdata, p_file, flg);
	
	emit_signal(SNAME("scene_saved"), p_file);
	_save_external_resources();
	editor_data.save_editor_external_data();
	for (Ref<AnimatedValuesBackup> &E : anim_backups) {
		E->restore();
	}
	if (err == OK) {
		scene->set_scene_file_path(ProjectSettings::get_singleton()->localize_path(p_file));
		editor_data.set_scene_as_saved(idx);
		editor_data.set_scene_modified_time(idx, FileAccess::get_modified_time(p_file));
		editor_folding.save_scene_folding(scene, p_file);
		_update_title();
		_update_scene_tabs();
	} else {
		_dialog_display_save_error(p_file, err);
	}
	scene->propagate_notification(NOTIFICATION_EDITOR_POST_SAVE);
}
void EditorNode::save_all_scenes() {