### 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
}
	}
	file->set_file_mode(EditorFileDialog::FILE_MODE_SAVE_FILE);
	saving_resource = p_resource;
	current_menu_option = RESOURCE_SAVE_AS;
	List<String> extensions;
	Ref<PackedScene> sd = memnew(PackedScene);
	ResourceSaver::get_recognized_extensions(p_resource, &extensions);
	file->clear_filters();
	List<String> preferred;
	for (const String &E : extensions) {
		if (p_resource->is_class("Script") && (E == "tres" || E == "res")) {
			
			continue;
		}
		file->add_filter("*." + E, E.to_upper());
		preferred.push_back(E);
	}
	
	List<String>::Element *res_element = preferred.find("res");
	if (res_element) {
		preferred.move_to_back(res_element);
	}
	
	List<String>::Element *tres_element = preferred.find("tres");
	if (tres_element) {
		preferred.move_to_front(tres_element);
	}
	if (!p_at_path.is_empty()) {
		file->set_current_dir(p_at_path);