ZK error message is shown on pressing "Esc' when deleting a Section/a Branch

1. Go to JCommune - Forum Structure, choose any Section, press "Delete"
2. Press "Esc" button on the keyboard
   As a Result, the following error mesage is shown:

Unknown exception: java.lang.NullPointerException.

Expected Result: "Delete Branch?" window should be closed, the deletion should be cancelled, Forum Structure Screen is to be shown

The same behavior happens when clicking "Esc" on deleting a Branch