### 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
label->set_text(p_res->get_name());
	} else {
		label->set_text(p_res->get_class());
	}
	drag_control->add_child(label);
	p_from->set_drag_preview(drag_control); 
	label->set_position(Point2((preview->get_width() - label->get_minimum_size().width) / 2, preview->get_height()));
	Dictionary drag_data;
	drag_data["type"] = "resource";
	drag_data["resource"] = p_res;
	drag_data["from"] = p_from;
	return drag_data;
}
Variant EditorNode::drag_files_and_dirs(const Vector<String> &p_paths, Control *p_from) {
	bool has_folder = false;
	bool has_file = false;
	for (int i = 0; i < p_paths.size(); i++) {
		bool is_folder = p_paths[i].ends_with("/");
		has_folder |= is_folder;
		has_file |= !is_folder;
	}
	int max_rows = 6;
	int num_rows = p_paths.size() > max_rows ? max_rows - 1 : p_paths.size(); 
	VBoxContainer *vbox = memnew(VBoxContainer);
	for (int i = 0; i < num_rows; i++) {
		HBoxContainer *hbox = memnew(HBoxContainer);
		TextureRect *icon = memnew(TextureRect);
		Label *label = memnew(Label);
		if (p_paths[i].ends_with("/")) {
			label->set_text(p_paths[i].substr(0, p_paths[i].length() - 1).get_file());