### 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
file_export_lib->get_vbox()->add_child(file_export_lib_apply_xforms);
	gui_base->add_child(file_export_lib);
	file_script = memnew(EditorFileDialog);
	file_script->set_title(TTR("Open & Run a Script"));
	file_script->set_access(EditorFileDialog::ACCESS_FILESYSTEM);
	file_script->set_file_mode(EditorFileDialog::FILE_MODE_OPEN_FILE);
	List<String> sexts;
	ResourceLoader::get_recognized_extensions_for_type("Script", &sexts);
	for (const String &E : sexts) {
		file_script->add_filter("*." + E);
	}
	gui_base->add_child(file_script);
	file_script->connect("file_selected", callable_mp(this, &EditorNode::_dialog_action));
	file_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
	file_menu->connect("about_to_popup", callable_mp(this, &EditorNode::_update_file_menu_opened));
	file_menu->connect("popup_hide", callable_mp(this, &EditorNode::_update_file_menu_closed));
	settings_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
	file->connect("file_selected", callable_mp(this, &EditorNode::_dialog_action));
	file_templates->connect("file_selected", callable_mp(this, &EditorNode::_dialog_action));
	audio_preview_gen = memnew(AudioStreamPreviewGenerator);
	add_child(audio_preview_gen);
	add_editor_plugin(memnew(DebuggerEditorPlugin(debug_menu)));
	disk_changed = memnew(ConfirmationDialog);
	{
		VBoxContainer *vbc = memnew(VBoxContainer);
		disk_changed->add_child(vbc);
		Label *dl = memnew(Label);
		dl->set_text(TTR("The following files are newer on disk.\nWhat action should be taken?"));
		vbc->add_child(dl);
		disk_changed_list = memnew(Tree);