### 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 (!p_ignore_broken_deps && dependency_errors.has(lpath)) {
		current_menu_option = -1;
		Vector<String> errors;
		for (const String &E : dependency_errors[lpath]) {
			errors.push_back(E);
		}
		dependency_error->show(DependencyErrorDialog::MODE_SCENE, lpath, errors);
		opening_prev = false;
		if (prev != -1) {
			set_current_scene(prev);
			editor_data.remove_scene(idx);
		}
		return ERR_FILE_MISSING_DEPENDENCIES;
	}
	dependency_errors.erase(lpath); 
	for (KeyValue<String, HashSet<String>> &E : dependency_errors) {
		String txt = vformat(TTR("Scene '%s' has broken dependencies:"), E.key) + "\n";
		for (const String &F : E.value) {
			txt += "\t" + F + "\n";
		}
		add_io_error(txt);
	}
	if (ResourceCache::has(lpath)) {
		
		Ref<PackedScene> ps = ResourceCache::get_ref(lpath);
		if (ps.is_valid()) {
			ps->replace_state(sdata->get_state());
			ps->set_last_modified_time(sdata->get_last_modified_time());
			sdata = ps;