How to set a dropdown to the blank line value

Hi all,

maybe a very easy question.

How can I set a dropdownbyindex value to the blank line?

If I use e.g.

wdContext.currentActionsElement().setDescription(null);

it adds another blank line among the values and if I try with:

wdContext.nodeActions().setLeadSelection(0);

it doesn't work.

Any suggestion?

Thanks in advance.

Angelo