### 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
main_menu->add_child(settings_menu);
	ED_SHORTCUT_AND_COMMAND("editor/editor_settings", TTR("Editor Settings..."));
	ED_SHORTCUT_OVERRIDE("editor/editor_settings", "macos", KeyModifierMask::META + Key::COMMA);
	settings_menu->add_shortcut(ED_GET_SHORTCUT("editor/editor_settings"), SETTINGS_PREFERENCES);
	settings_menu->add_shortcut(ED_SHORTCUT("editor/command_palette", TTR("Command Palette..."), KeyModifierMask::CMD_OR_CTRL | KeyModifierMask::SHIFT | Key::P), HELP_COMMAND_PALETTE);
	settings_menu->add_separator();
	editor_layouts = memnew(PopupMenu);
	editor_layouts->set_name("Layouts");
	editor_layouts->set_auto_translate(false);
	settings_menu->add_child(editor_layouts);
	editor_layouts->connect("id_pressed", callable_mp(this, &EditorNode::_layout_menu_option));
	settings_menu->add_submenu_item(TTR("Editor Layout"), "Layouts");
	settings_menu->add_separator();
	ED_SHORTCUT_AND_COMMAND("editor/take_screenshot", TTR("Take Screenshot"), KeyModifierMask::CTRL | Key::F12);
	ED_SHORTCUT_OVERRIDE("editor/take_screenshot", "macos", KeyModifierMask::META | Key::F12);
	settings_menu->add_shortcut(ED_GET_SHORTCUT("editor/take_screenshot"), EDITOR_SCREENSHOT);
	settings_menu->set_item_tooltip(-1, TTR("Screenshots are stored in the Editor Data/Settings Folder."));
#ifndef ANDROID_ENABLED
	ED_SHORTCUT_AND_COMMAND("editor/fullscreen_mode", TTR("Toggle Fullscreen"), KeyModifierMask::SHIFT | Key::F11);
	ED_SHORTCUT_OVERRIDE("editor/fullscreen_mode", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::F);
	settings_menu->add_shortcut(ED_GET_SHORTCUT("editor/fullscreen_mode"), SETTINGS_TOGGLE_FULLSCREEN);
#endif
	settings_menu->add_separator();
#ifndef ANDROID_ENABLED
	if (OS::get_singleton()->get_data_path() == OS::get_singleton()->get_config_path()) {
		
		settings_menu->add_item(TTR("Open Editor Data/Settings Folder"), SETTINGS_EDITOR_DATA_FOLDER);
	} else {
		
		settings_menu->add_item(TTR("Open Editor Data Folder"), SETTINGS_EDITOR_DATA_FOLDER);