Thanks for writing to us and your report.
This seems to be a glitch in the treeview control. After the node has been removed, the treeview tries to toggle it and hence the problem appears. Unfortunately, there is no way to cancel the toggle action at this moment. I would suggest that you use the OnClientNodeClicking
event instead the OnClientDoubleClick.
I logged this issue in our Bug Tracking system so that our developers can solve the problem with the official Q1 release due in April.
Your Telerik points have been updated for your report.
the Telerik team