### 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
recent_scenes->connect("id_pressed", callable_mp(this, &EditorNode::_open_recent_scene));
	if (!global_menu || !OS::get_singleton()->has_feature("macos")) {
		
		file_menu->add_separator();
		file_menu->add_shortcut(ED_SHORTCUT_AND_COMMAND("editor/file_quit", TTR("Quit"), KeyModifierMask::CMD_OR_CTRL + Key::Q), FILE_QUIT, true);
	}
	project_menu = memnew(PopupMenu);
	project_menu->set_name(TTR("Project"));
	main_menu->add_child(project_menu);
	project_menu->add_shortcut(ED_SHORTCUT_AND_COMMAND("editor/project_settings", TTR("Project Settings..."), Key::NONE, TTR("Project Settings")), RUN_SETTINGS);
	project_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
	project_menu->add_separator();
	project_menu->add_item(TTR("Version Control"), VCS_MENU);
	project_menu->add_separator();
	project_menu->add_shortcut(ED_SHORTCUT_AND_COMMAND("editor/export", TTR("Export..."), Key::NONE, TTR("Export")), FILE_EXPORT_PROJECT);
#ifndef ANDROID_ENABLED
	project_menu->add_item(TTR("Install Android Build Template..."), FILE_INSTALL_ANDROID_SOURCE);
	project_menu->add_item(TTR("Open User Data Folder"), RUN_USER_DATA_FOLDER);
#endif
	project_menu->add_separator();
	project_menu->add_item(TTR("Customize Engine Build Configuration..."), TOOLS_BUILD_PROFILE_MANAGER);
	project_menu->add_separator();
	plugin_config_dialog = memnew(PluginConfigDialog);
	plugin_config_dialog->connect("plugin_ready", callable_mp(this, &EditorNode::_on_plugin_ready));
	gui_base->add_child(plugin_config_dialog);
	tool_menu = memnew(PopupMenu);
	tool_menu->set_name("Tools");
	tool_menu->connect("index_pressed", callable_mp(this, &EditorNode::_tool_menu_option));
	project_menu->add_child(tool_menu);
	project_menu->add_submenu_item(TTR("Tools"), "Tools");