### 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
exiting = true;
	if (project_run_bar->is_playing()) {
		project_run_bar->stop_playing();
	}
	String to_reopen;
	if (get_tree()->get_edited_scene_root()) {
		to_reopen = get_tree()->get_edited_scene_root()->get_scene_file_path();
	}
	_exit_editor(EXIT_SUCCESS);
	List<String> args;
	for (const String &a : Main::get_forwardable_cli_arguments(Main::CLI_SCOPE_TOOL)) {
		args.push_back(a);
	}
	args.push_back("--path");
	args.push_back(ProjectSettings::get_singleton()->get_resource_path());
	args.push_back("-e");
	if (!to_reopen.is_empty()) {
		args.push_back(to_reopen);
	}
	OS::get_singleton()->set_restart_on_exit(true, args);
}
void EditorNode::_save_all_scenes() {