Defendants' further ground was waived by their failure to raise it at trial. Accord, Walraven v. Walraven, 243 Ga. 487 ( 254 S.E.2d 863) (1979); Abrams v. Abrams, 239 Ga. 866 ( 239 S.E.2d 33) (1977); Thompson v. Lagerquist, 232 Ga. 75 ( 205 S.E.2d 267) (1974). 2.