The Playmaker has saddled up to handle international sales duties for Sonja Maria Kröner’s family adventure film “Horse on a Stick,” which will have its market premiere at Cannes Film Market. The film, which opens in German theaters on April 23, distributed by Port au Prince, is produced by Lieblingsfilm, whose previous production, comedy “Extrawurst,” is Germany’s most successful box office release of this year so far, with a $21.9 million gross from 1.9 million admissions. “Horse on a Stick”