### 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
InspectorDock::get_singleton()->edit_resource(p_resource);
}
void EditorNode::save_resource_in_path(const Ref<Resource> &p_resource, const String &p_path) {
	editor_data.apply_changes_in_editors();
	if (saving_resources_in_path.has(p_resource)) {
		return;
	}
	saving_resources_in_path.insert(p_resource);
	int flg = 0;
	if (EDITOR_GET("filesystem/on_save/compress_binary_resources")) {
		flg |= ResourceSaver::FLAG_COMPRESS;
	}
	String path = ProjectSettings::get_singleton()->localize_path(p_path);
	Error err = ResourceSaver::save(p_resource, path, flg | ResourceSaver::FLAG_REPLACE_SUBRESOURCE_PATHS);
	if (err != OK) {
		if (ResourceLoader::is_imported(p_resource->get_path())) {
			show_accept(TTR("Imported resources can't be saved."), TTR("OK"));
		} else {
			show_accept(TTR("Error saving resource!"), TTR("OK"));
		}
		saving_resources_in_path.erase(p_resource);
		return;
	}
	((Resource *)p_resource.ptr())->set_path(path);
	saving_resources_in_path.erase(p_resource);
	_resource_saved(p_resource, path);
	emit_signal(SNAME("resource_saved"), p_resource);
	editor_data.notify_resource_saved(p_resource);
}
void EditorNode::save_resource(const Ref<Resource> &p_resource) {