Movie theater stocks took a beating Wednesday after AMC Entertainment previewed a grim earnings report. AMC’s announcement came amid broader pessimism about what has been a lackluster summer movie season. AMC shares lost nearly a quarter of their value a day after the company’s announcement late Tuesday that its U.S. box office receipts tumbled 4.4 percent in the second quarter. A disappointing summer at the box office has put pressure on major North American theater chains, which split grosses with Hollywood studios. Due to dearth of major summer hits outside of “Wonder Woman” and “Guardians of the Galaxy, Vol.