### 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 (!scene_path.is_empty()) {
						required_load_paths.push_front(scene_path);
					}
					Ref<SceneState> inherited_state = original_node->get_scene_inherited_state();
					while (inherited_state.is_valid()) {
						String inherited_path = inherited_state->get_path();
						
						if (!inherited_path.is_empty()) {
							required_load_paths.push_front(inherited_path);
						}
						inherited_state = inherited_state->get_base_scene_state();
					}
					
					
					for (String path : required_load_paths) {
						if (!local_scene_cache.find(path)) {
							current_packed_scene = ResourceLoader::load(path, "", ResourceFormatLoader::CACHE_MODE_IGNORE, &err);
							current_packed_scene->set_path(path, true);
							local_scene_cache[path] = current_packed_scene;
						} else {
							current_packed_scene = local_scene_cache[path];
						}
					}
				}
				ERR_FAIL_COND(current_packed_scene.is_null());
				
				Node *instantiated_node = nullptr;
				if (current_packed_scene.is_valid()) {
					instantiated_node = current_packed_scene->instantiate(PackedScene::GEN_EDIT_STATE_INSTANCE);
				}