### 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 (!keysym.is_empty()) {
						key_label = fix_key_label(keysym[0], keycode);
					}
				}
				if (keycode != Key::SHIFT) {
					k->set_shift_pressed(ke.shift);
				}
				if (keycode != Key::ALT) {
					k->set_alt_pressed(ke.alt);
				}
				if (keycode != Key::CTRL) {
					k->set_ctrl_pressed(ke.control);
				}
				if (keycode != Key::META) {
					k->set_meta_pressed(ke.meta);
				}
				k->set_keycode(keycode);
				k->set_physical_keycode(physical_keycode);
				k->set_key_label(key_label);
				if (i + 1 < key_event_pos && key_event_buffer[i + 1].uMsg == WM_CHAR) {
					char32_t unicode = key_event_buffer[i + 1].wParam;
					static char32_t prev_wck = 0;
					if ((unicode & 0xfffffc00) == 0xd800) {
						if (prev_wck != 0) {
							ERR_PRINT("invalid utf16 surrogate input");
						}
						prev_wck = unicode;
						break; 
					} else if ((unicode & 0xfffffc00) == 0xdc00) {
						if (prev_wck == 0) {