[PanelSpriteButton] Issue short description

[cat-sudo-format]

Is there an existing issue for this?

• [x] I have searched the existing issues

Enter the name of the extension

PanelSpriteButton

Describe the bug of the extension

the buttons that haved older version of extension without variants is broke and display no text

Steps to reproduce

1. go to project when you used buttons with older version
2. see the buttons in preview
3. buttons will display nothing

GDevelop platform

Desktop

GDevelop version

5.5.237

Platform info

OS: Windows

OS Ver.: Windows 10 (RS5, Core Single Language)

Additional context

[D8H]

Before you updated the extension you must have seen this red alert which links to this documentation:

• https://wiki.gdevelop.io/gdevelop5/objects/custom-objects-prefab-template/migrate-to-variants/

Please, try to follow the migration documentation.