Beginning July 18 the Gene Siskel Film Center will host the theatrical debut of “Indestructible,” a film directed by Ben Byer, whose life had been claimed earlier this month by Lou Gehrig’s disease (ALS), a disease for which a cure is just as much a mystery as its contraction. “Everything in the film is all him,” says his sister and the film’s producer, Rebeccah Rush. “He was doing that up to the day he died.” A milestone for a community that has, until now, received limited attention, the film follows the global travels of an answer-seeking Byer throughout the first three years of his diagnosis. “Even in the face of tragedy, Ben could still laugh, smile and move forward, and that sticks with people.” Rebeccah continues, “If there are people who hate the film, I don’t know who they are.”