Just a heads up.

The update for the latest libgdx framework 2 days ago leads to a bug where 'null' set attachments on the first frame of a timeline do not successfully 'hide' on animation state change.

I have temp fixed this for my project by reverting this line of code in the animation.java file:

skeleton.slots.get(slotIndex).attachmentName = attachmentName;

Reverted to:

skeleton.slots.get(slotIndex).setAttachment(attachmentName == null ? null : skeleton.getAttachment(slotIndex, attachmentName));

I hope you find time to solve this issue for others