### 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
OS::get_singleton()->shell_show_in_file_manager(OS::get_singleton()->get_user_data_dir(), true);
		} break;
		case FILE_EXPLORE_ANDROID_BUILD_TEMPLATES: {
			OS::get_singleton()->shell_show_in_file_manager(ProjectSettings::get_singleton()->get_resource_path().path_join("android"), true);
		} break;
		case FILE_QUIT:
		case RUN_PROJECT_MANAGER:
		case RELOAD_CURRENT_PROJECT: {
			if (p_confirmed && plugin_to_save) {
				plugin_to_save->save_external_data();
				p_confirmed = false;
			}
			if (!p_confirmed) {
				bool save_each = EDITOR_GET("interface/editor/save_each_scene_on_quit");
				if (_next_unsaved_scene(!save_each) == -1) {
					if (EditorUndoRedoManager::get_singleton()->is_history_unsaved(EditorUndoRedoManager::GLOBAL_HISTORY)) {
						if (p_option == RELOAD_CURRENT_PROJECT) {
							save_confirmation->set_ok_button_text(TTR("Save & Reload"));
							save_confirmation->set_text(TTR("Save modified resources before reloading?"));
						} else {
							save_confirmation->set_ok_button_text(TTR("Save & Quit"));
							save_confirmation->set_text(TTR("Save modified resources before closing?"));
						}
						save_confirmation->reset_size();
						save_confirmation->popup_centered();
						break;
					}
					plugin_to_save = nullptr;
					for (int i = 0; i < editor_data.get_editor_plugin_count(); i++) {
						const String unsaved_status = editor_data.get_editor_plugin(i)->get_unsaved_status();