I tried the example project,
Step 1 : Expand the first row(Phones),
Step 2 : Adding children to parent (Phones)
Step 3 : Collapse the parent (Phones)
Step 4 : Expand Same parent (Phones), it crashed the app says :

"fatal error: unexpectedly found nil while unwrapping an Optional value"

in "func treeView(treeView: RATreeView, cellForItem item: AnyObject?) -> UITableViewCell"
Where in "item" value itself is nil

Any possible work around why its crashing?