### 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)

FreeLibrary(nt_lib);
	}
	
	HMODULE ux_theme_lib = LoadLibraryW(L"uxtheme.dll");
	if (ux_theme_lib) {
		ShouldAppsUseDarkMode = (ShouldAppsUseDarkModePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(132));
		GetImmersiveColorFromColorSetEx = (GetImmersiveColorFromColorSetExPtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(95));
		GetImmersiveColorTypeFromName = (GetImmersiveColorTypeFromNamePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(96));
		GetImmersiveUserColorSetPreference = (GetImmersiveUserColorSetPreferencePtr)GetProcAddress(ux_theme_lib, MAKEINTRESOURCEA(98));
		ux_theme_available = ShouldAppsUseDarkMode && GetImmersiveColorFromColorSetEx && GetImmersiveColorTypeFromName && GetImmersiveUserColorSetPreference;
		if (os_ver.dwBuildNumber >= 22000) {
			dark_title_available = true;
		}
	}
	
	HMODULE wintab_lib = LoadLibraryW(L"wintab32.dll");
	if (wintab_lib) {
		wintab_WTOpen = (WTOpenPtr)GetProcAddress(wintab_lib, "WTOpenW");
		wintab_WTClose = (WTClosePtr)GetProcAddress(wintab_lib, "WTClose");
		wintab_WTInfo = (WTInfoPtr)GetProcAddress(wintab_lib, "WTInfoW");
		wintab_WTPacket = (WTPacketPtr)GetProcAddress(wintab_lib, "WTPacket");
		wintab_WTEnable = (WTEnablePtr)GetProcAddress(wintab_lib, "WTEnable");
		wintab_available = wintab_WTOpen && wintab_WTClose && wintab_WTInfo && wintab_WTPacket && wintab_WTEnable;
	}
	if (wintab_available) {
		tablet_drivers.push_back("wintab");
	}
	
	
	HMODULE user32_lib = LoadLibraryW(L"user32.dll");