### 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
ERR_FAIL_COND_V(!p_object, false);
	Ref<Script> scr = p_object->get_script();
	if (scr.is_null() && Object::cast_to<Script>(p_object)) {
		scr = p_object;
	}
	if (scr.is_valid()) {
		Ref<Script> base_script = scr;
		while (base_script.is_valid()) {
			StringName name = EditorNode::get_editor_data().script_class_get_name(base_script->get_path());
			if (name == p_class) {
				return true;
			}
			base_script = base_script->get_base_script();
		}
	}
	return false;
}
void EditorNode::progress_add_task(const String &p_task, const String &p_label, int p_steps, bool p_can_cancel) {
	if (singleton->cmdline_export_mode) {
		print_line(p_task + ": begin: " + p_label + " steps: " + itos(p_steps));
	} else if (singleton->progress_dialog) {
		singleton->progress_dialog->add_task(p_task, p_label, p_steps, p_can_cancel);
	}
}
bool EditorNode::progress_task_step(const String &p_task, const String &p_state, int p_step, bool p_force_refresh) {