With production on Fantastic Beasts 3 pushed to the end of the year, Ezra Miller has found himself with an open slot this summer, but instead of finally making The Flash movie, he has signed on to star in the indie thriller The Mourner, it was announced Tuesday. Casper Kiriya (Casshern) is set to direct from a script by Robin Shushan (AMC’s Feed the Beast), who adapted the Japanese novel Itamu Hito by Arata Tendo. The book was previously adapted as a Japanese-language film in 2015. Kiriya will also produce alongside Mike Marcus (You Kill Me) of Echo …