Based on the crash it looks like you’re hitting this assert in SPathView: check(SelectedItems.Num() > 0);.
This is a crash that was recently fixed for 4.12. If you’re building the engine from source then you can remove the assert and replace it with an if check instead:
// Send the first selected item with the notification
const TArray<TSharedPtr<FTreeItem>> SelectedItems = TreeViewPtr->GetSelectedItems();
if (SelectedItems.Num() > 0)
{
// Signal a single selection changed event to let any listeners know that paths have changed
TreeSelectionChanged( SelectedItems[0], ESelectInfo::Direct );
}