### 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
return;
		}
		Ref<InputEventMouseButton> mb = me;
		if (mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && mb->is_pressed() && dock_popup_selected_idx != nrect) {
			Control *dock = dock_slot[dock_popup_selected_idx]->get_current_tab_control();
			if (dock) {
				dock_slot[dock_popup_selected_idx]->remove_child(dock);
			}
			if (dock_slot[dock_popup_selected_idx]->get_tab_count() == 0) {
				dock_slot[dock_popup_selected_idx]->hide();
			} else {
				dock_slot[dock_popup_selected_idx]->set_current_tab(0);
			}
			dock_slot[nrect]->add_child(dock);
			dock_popup_selected_idx = nrect;
			dock_slot[nrect]->set_current_tab(dock_slot[nrect]->get_tab_count() - 1);
			dock_slot[nrect]->set_tab_title(dock_slot[nrect]->get_tab_count() - 1, TTRGET(dock->get_name()));
			dock_slot[nrect]->show();
			dock_select->queue_redraw();
			_update_dock_containers();
			_edit_current();
			_save_editor_layout();
		}
	}
}
void EditorNode::_dock_popup_exit() {
	dock_select_rect_over_idx = -1;
	dock_select->queue_redraw();
}
void EditorNode::_dock_pre_popup(int p_which) {