### 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)

_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	DWORD style = 0;
	DWORD style_ex = 0;
	_get_window_style(p_window == MAIN_WINDOW_ID, wd.fullscreen, wd.multiwindow_fs, wd.borderless, wd.resizable, wd.maximized, wd.no_focus || wd.is_popup, style, style_ex);
	SetWindowLongPtr(wd.hWnd, GWL_STYLE, style);
	SetWindowLongPtr(wd.hWnd, GWL_EXSTYLE, style_ex);
	if (icon.is_valid()) {
		set_icon(icon);
	}
	SetWindowPos(wd.hWnd, wd.always_on_top ? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | ((wd.no_focus || wd.is_popup) ? SWP_NOACTIVATE : 0));
	if (p_repaint) {
		RECT rect;
		GetWindowRect(wd.hWnd, &rect);
		MoveWindow(wd.hWnd, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, TRUE);
	}
}
void DisplayServerWindows::window_set_mode(WindowMode p_mode, WindowID p_window) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	if (wd.fullscreen && p_mode != WINDOW_MODE_FULLSCREEN && p_mode != WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
		RECT rect;
		wd.fullscreen = false;
		wd.multiwindow_fs = false;
		wd.maximized = wd.was_maximized;
		_update_window_style(p_window, false);
		if (wd.pre_fs_valid) {