SPOILER ALERT:  This story contains spoilers for the Season 9 finale of ABC’s “ 9-1-1 ,” titled “Hearts and Flowers.” “9-1-1” ended its ninth season Thursday with two big changes heading into Season 10: Athena (Angela Bassett) is finally becoming a detective — and Buck ( Oliver Stark ) might become a father. In the final moments of the “9-1-1” Season 9 finale, it was revealed that Buck has taken in preschooler Theo and will be fostering him after the unexpected car-crash death of Theo’s parents (who were Buck’s good friends). Theo is technically Buck’s biological son — but Buck previously wanted as little to do with the child as possible, given that he was the sperm donor for his friends and didn’t intend to be part of Theo’s life. So, is he stepping in now because there’s no one else — or because he’s potentially interested in actually becoming the adoptive father to his biological son? Popular on Variety “Like most decisions, it’s a little bit of both, right?…