Keyboard interaction for treeview does not indicate what to do when the first child node is disabled

[marjonlynch]

When traversing a tree-view with the keyboard, hitting the right arrow key on a node with children specifies to first expand the tree and then if right arrow key is hit again to focus the first child node. It does not specify what to do when that first node is disabled. Presumably the instruction would be to focus the first non-disabled child node.

https://w3c.github.io/aria-practices/#keyboard-interaction-23

Right arrow:
When focus is on a closed node, opens the node; focus does not move.
When focus is on a open node, moves focus to the first child node.
When focus is on an end node, does nothing.