checking a radiobuttonlist FIRST to avoid ERROR..

I have the following line of code:
selecteditems.Add((cntr.FindControl("rbFederalClassifications") as RadioButtonList).SelectedItem.Text);
If I submit the page.. and no radio buttons were selected I get an error that 'object not set to an instance' ... is there a 'quick and easy' way to say ... if 'NO ITEMS WERE SELECTED' .. skip this... basically.. IF NULL... skip?

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