The director of “The Strangers” is back with another scary cautionary tale about keeping your door locked If I’ve learned anything from watching Bryan Bertino movies it’s that I should never, ever open my door. For anybody. Sorry, trick ‘r treaters, you’ll have to ply your trade elsewhere. Sorry, pizza delivery person, I’m not falling for that old gag. Sorry, Publisher’s Clearing House, I don’t need a million dollars that badly … Wait! No! I was kidding! It was just an opening paragraph gag, I…