### 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
gdextension_export_plugin.instantiate();
	EditorExport::get_singleton()->add_export_plugin(gdextension_export_plugin);
	Ref<DedicatedServerExportPlugin> dedicated_server_export_plugin;
	dedicated_server_export_plugin.instantiate();
	EditorExport::get_singleton()->add_export_plugin(dedicated_server_export_plugin);
	Ref<PackedSceneEditorTranslationParserPlugin> packed_scene_translation_parser_plugin;
	packed_scene_translation_parser_plugin.instantiate();
	EditorTranslationParser::get_singleton()->add_parser(packed_scene_translation_parser_plugin, EditorTranslationParser::STANDARD);
	_edit_current();
	current = nullptr;
	saving_resource = Ref<Resource>();
	set_process(true);
	open_imported = memnew(ConfirmationDialog);
	open_imported->set_ok_button_text(TTR("Open Anyway"));
	new_inherited_button = open_imported->add_button(TTR("New Inherited"), !DisplayServer::get_singleton()->get_swap_cancel_ok(), "inherit");
	open_imported->connect("confirmed", callable_mp(this, &EditorNode::_open_imported));
	open_imported->connect("custom_action", callable_mp(this, &EditorNode::_inherit_imported));
	gui_base->add_child(open_imported);
	quick_open = memnew(EditorQuickOpen);
	gui_base->add_child(quick_open);
	quick_open->connect("quick_open", callable_mp(this, &EditorNode::_quick_opened));
	_update_recent_scenes();
	set_process_shortcut_input(true);
	load_errors = memnew(RichTextLabel);
	load_error_dialog = memnew(AcceptDialog);
	load_error_dialog->set_unparent_when_invisible(true);
	load_error_dialog->add_child(load_errors);
	load_error_dialog->set_title(TTR("Load Errors"));
	execute_outputs = memnew(RichTextLabel);
	execute_outputs->set_selection_enabled(true);