We knew he was trouble! Harry Styles announced that his new album, Fine Line, drops on Dec. 13 – which, as everyone in the world knows, is his ex Taylor Swift’s birthday. (Her 30th, no less!) Their respective fans, naturally, have gone berserk. “Harry cannot have forgotten Taylor’s birthday. There’s no way it’s a coincidence,” insisted one, while another fretted, “There must be songs about Taylor.” Sure, because the 25-year-old pop star dated her for three months almost seven years ago. (Her 2015 tunes “Style” and “Out of the Woods” were reportedly inspired by him.) Still others saw it as proof of a “Haylor collab” on a track…or even a rekindled romance, despite her serious three-year relationship with Joe Alwyn. One thing we can definitely assume? Taylor’s going to write…