### 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
accept->queue_free();
			}
			if (save_accept) {
				save_accept->queue_free();
			}
			editor_data.save_editor_external_data();
			FileAccess::set_file_close_fail_notify_callback(nullptr);
			log->deinit(); 
			editor_data.clear_edited_scenes();
		} break;
		case NOTIFICATION_READY: {
			{
				_initializing_plugins = true;
				Vector<String> addons;
				if (ProjectSettings::get_singleton()->has_setting("editor_plugins/enabled")) {
					addons = GLOBAL_GET("editor_plugins/enabled");
				}
				for (int i = 0; i < addons.size(); i++) {
					set_addon_plugin_enabled(addons[i], true);
				}
				_initializing_plugins = false;
				if (!pending_addons.is_empty()) {
					EditorFileSystem::get_singleton()->connect("script_classes_updated", callable_mp(this, &EditorNode::_enable_pending_addons));
				}
			}
			RenderingServer::get_singleton()->viewport_set_disable_2d(get_scene_root()->get_viewport_rid(), true);
			RenderingServer::get_singleton()->viewport_set_environment_mode(get_viewport()->get_viewport_rid(), RenderingServer::VIEWPORT_ENVIRONMENT_DISABLED);
			feature_profile_manager->notify_changed();
			_select_default_main_screen_plugin();