Screenwriter Melissa Mathison (E.T.), who's been married to Harrison Ford for 12 years, says that despite fame, their life is pretty garden-variety. ''We're just like any husband and wife,'' says Mathison, who penned this summer's The Indian and the Cupboard. So when a romantic photo of Ford and Julia Ormond, his Sabrina costar, hit the scandal pages of a European newspaper this spring, the couple did what they always do. They ignored it. ''Harrison doesn't attract that kind of innuendo much,'' she says. ''He's lucky.'' Mathison explains that the photo was actually done for Sabrina. ''They were shooting a love scene on a bridge in Paris,'' she says, adding that the funniest part was reading how she rushed to Paris as ''the avenging wife.'' So, has the duo who have a son, Malcolm, 8, and a daughter, Georgia, 5 ever considered collaborating on a film? ''I have a script he wants to do,'' says Mathison of her 53-year-old husband. ''It's about a father. But Harrison wants to wait until he's older.''