### 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
int flg = 0;
	if (EDITOR_GET("filesystem/on_save/compress_binary_resources")) {
		flg |= ResourceSaver::FLAG_COMPRESS;
	}
	flg |= ResourceSaver::FLAG_REPLACE_SUBRESOURCE_PATHS;
	HashSet<String> edited_resources;
	int saved = 0;
	List<Ref<Resource>> cached;
	ResourceCache::get_cached_resources(&cached);
	for (Ref<Resource> res : cached) {
		if (!res->is_edited()) {
			continue;
		}
		String path = res->get_path();
		if (path.begins_with("res:")) {
			int subres_pos = path.find("::");
			if (subres_pos == -1) {
				
				edited_resources.insert(path);
			} else {
				edited_resources.insert(path.substr(0, subres_pos));
			}
		}