No error in either the admission or the exclusion of evidence, and no error or defect in any ruling or order or in anything done or omitted by the court or by any of the parties, is ground for granting a new trial or otherwise disturbing a judgment or order, unless refusal to take such action appears to the court inconsistent with substantial justice. The court at every stage of the proceeding must disregard any error or defect in the proceeding which does not affect the substantial rights of the parties.