[Steps]
1. Create a Calc doc.
2. Select any cell, input "=SUM(xx)", where xx represent a coordinate of a cell,
such as D3. Then press ENTER to finish the editting.
3. Press the black triangle beside the Undo button in Standard toolbar to show
the drop-list of Undo.
4. Double-click the cell which edited in step 2 to enter edit-mode, then operate
step3 again.
5, Without quiting the edit-mode, press Undo button for several times.

[Result]
1. In step 3, the drop-list of Undo has only one item -- Input.(This is correct)
2. In step 4, the drop-list of Undo has 3 dup items.
3. In step 5, the Undo has no effect except the cursor jump between the parentheses.