### 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 (lpb == nullptr) {
				return 0;
			}
			if (GetRawInputData((HRAWINPUT)lParam, RID_INPUT, lpb, &dwSize, sizeof(RAWINPUTHEADER)) != dwSize) {
				OutputDebugString(TEXT("GetRawInputData does not return correct size !\n"));
			}
			RAWINPUT *raw = (RAWINPUT *)lpb;
			if (raw->header.dwType == RIM_TYPEMOUSE) {
				Ref<InputEventMouseMotion> mm;
				mm.instantiate();
				mm->set_window_id(window_id);
				mm->set_ctrl_pressed(control_mem);
				mm->set_shift_pressed(shift_mem);
				mm->set_alt_pressed(alt_mem);
				mm->set_pressure((raw->data.mouse.ulButtons & RI_MOUSE_LEFT_BUTTON_DOWN) ? 1.0f : 0.0f);
				mm->set_button_mask(last_button_state);
				Point2i c(windows[window_id].width / 2, windows[window_id].height / 2);
				
				POINT pos = { (int)c.x, (int)c.y };
				ClientToScreen(windows[window_id].hWnd, &pos);
				SetCursorPos(pos.x, pos.y);
				mm->set_position(c);
				mm->set_global_position(c);
				mm->set_velocity(Vector2(0, 0));
				if (raw->data.mouse.usFlags == MOUSE_MOVE_RELATIVE) {
					mm->set_relative(Vector2(raw->data.mouse.lLastX, raw->data.mouse.lLastY));
				} else if (raw->data.mouse.usFlags == MOUSE_MOVE_ABSOLUTE) {
					int nScreenWidth = GetSystemMetrics(SM_CXVIRTUALSCREEN);
					int nScreenHeight = GetSystemMetrics(SM_CYVIRTUALSCREEN);
					int nScreenLeft = GetSystemMetrics(SM_XVIRTUALSCREEN);