### 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)

k->set_key_label(key_label);
					k->set_unicode(fix_unicode(unicode));
					if (k->get_unicode() && gr_mem) {
						k->set_alt_pressed(false);
						k->set_ctrl_pressed(false);
					}
					Input::get_singleton()->parse_input_event(k);
				} else {
					
				}
			} break;
			case WM_KEYUP:
			case WM_KEYDOWN: {
				Ref<InputEventKey> k;
				k.instantiate();
				k->set_window_id(ke.window_id);
				k->set_pressed(ke.uMsg == WM_KEYDOWN);
				Key keycode = KeyMappingWindows::get_keysym(ke.wParam);
				if ((ke.lParam & (1 << 24)) && (ke.wParam == VK_RETURN)) {
					
					keycode = Key::KP_ENTER;
				}
				Key key_label = keycode;
				Key physical_keycode = KeyMappingWindows::get_scansym((ke.lParam >> 16) & 0xFF, ke.lParam & (1 << 24));
				static BYTE keyboard_state[256];
				memset(keyboard_state, 0, 256);
				wchar_t chars[256] = {};
				UINT extended_code = MapVirtualKey((ke.lParam >> 16) & 0xFF, MAPVK_VSC_TO_VK_EX);
				if (!(ke.lParam & (1 << 24)) && ToUnicodeEx(extended_code, (ke.lParam >> 16) & 0xFF, keyboard_state, chars, 255, 4, GetKeyboardLayout(0)) > 0) {
					String keysym = String::utf16((char16_t *)chars, 255);