(a) If duly demanded, a party is entitled to trial by jury in a formal testacy proceeding and any proceeding in which any controverted question of fact arises as to which any party has a constitutional right to trial by jury.
(b) If there is no right to trial by jury under subsection (a) or the right is waived, the court in its discretion may call a jury to decide any issue of fact, in which case the verdict is advisory only.