reproducing steps

1. open display.zul
2. right click on sheet tab ""cell-text"" and protect sheet/rename/move (not delete)
3. right click on sheet tab ""cell-text"" and try unprotect sheet

expected:
sheet is unprotected

actual:
nothing happens

extra information

if you right click on sheet tab, select "delete" at the first time. You can keep deleting sheets via context menu. but other operation on context menu don't work.