### 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
Ref<DirAccess> dir = DirAccess::create(DirAccess::ACCESS_FILESYSTEM);
	for (int i = 0; i < p_files.size(); i++) {
		String from = p_files[i];
		String to = to_path.path_join(from.get_file());
		if (dir->dir_exists(from)) {
			Vector<String> sub_files;
			Ref<DirAccess> sub_dir = DirAccess::open(from);
			sub_dir->list_dir_begin();
			String next_file = sub_dir->get_next();
			while (!next_file.is_empty()) {
				if (next_file == "." || next_file == "..") {
					next_file = sub_dir->get_next();
					continue;
				}
				sub_files.push_back(from.path_join(next_file));
				next_file = sub_dir->get_next();
			}
			if (!sub_files.is_empty()) {
				dir->make_dir(to);
				_add_dropped_files_recursive(sub_files, to);
			}
			continue;
		}
		dir->copy(from, to);
	}
}
void EditorNode::_file_access_close_error_notify(const String &p_str) {