Changes in constitution of Benches

407[350A. No order or judgment of a Bench of Magistrates shall be invalid by reason only of a change having occurred in the constitution of the Bench in any case in which the Bench by which such order or judgment is passed is duly constituted under 408[section 15 and 16 or, as the case may be, section 19 and 21] , and the Magistrates constituting the same have been present on the Bench throughout the proceedings.]