(a) An attorney shall not act as advocate at a trial in which the attorney is likely to be a necessary witness unless:

(1) the testimony relates to an uncontested issue;

(2) the testimony relates to the nature and value of legal services rendered in the case; or

(3) disqualification of the attorney would work substantial hardship on the client.

(b) An attorney may act as advocate in a trial in which another attorney in the attorney's firm is likely to be called as a witness unless precluded from doing so by Rule 19-301.7 (1.7) or Rule 19-301.9 (1.9).