### Godot version

Godot Engine v4.0.stable.official.92bee43ad

### System information

Windows 10

### Issue description

The documentation states that passing ```null``` into the image parameter of ```set_custom_mouse_cursor``` will change it back to the system cursor, however I find that it removes the cursor's image entirely, rather than setting it to the system's cursor.


### Steps to reproduce

```var isimage = false
var theimage = load("res://final.png")

func _on_my_button_pressed():
    if isimage == false:
        Input.set_custom_mouse_cursor(theimage, Input.CURSOR_ARROW, Vector2(16,16))
        isimage = true
        
    else:
        Input.set_custom_mouse_cursor(null)
        isimage = false```

When the button is pressed, the cursor is meant to change to the new cursor. When it has been pressed a second time, it changes back to the default cursor. However, upon pressing it a second time, it simply disappears. The cursor becomes visible again when the cursor exits and re-enters the window.

### Minimal reproduction project

[null mouse.zip](https://github.com/godotengine/godot/files/10901969/null.mouse.zip)

if (windows[window_id].resizable && !windows[window_id].fullscreen) {
				
				Size2 decor = window_get_size_with_decorations(window_id) - window_get_size(window_id);
				MINMAXINFO *min_max_info = (MINMAXINFO *)lParam;
				if (windows[window_id].min_size != Size2()) {
					min_max_info->ptMinTrackSize.x = windows[window_id].min_size.x + decor.x;
					min_max_info->ptMinTrackSize.y = windows[window_id].min_size.y + decor.y;
				}
				if (windows[window_id].max_size != Size2()) {
					min_max_info->ptMaxTrackSize.x = windows[window_id].max_size.x + decor.x;
					min_max_info->ptMaxTrackSize.y = windows[window_id].max_size.y + decor.y;
				}
				return 0;
			}
		} break;
		case WM_ERASEBKGND: {
			Color early_color;
			if (!_get_window_early_clear_override(early_color)) {
				break;
			}
			bool must_recreate_brush = !window_bkg_brush || window_bkg_brush_color != early_color.to_argb32();
			if (must_recreate_brush) {
				if (window_bkg_brush) {
					DeleteObject(window_bkg_brush);
				}
				window_bkg_brush = CreateSolidBrush(RGB(early_color.get_r8(), early_color.get_g8(), early_color.get_b8()));
			}
			HDC hdc = (HDC)wParam;
			RECT rect = {};
			if (GetUpdateRect(hWnd, &rect, true)) {