“Third Person,” the latest interlocking drama from “Crash” writer-director Paul Haggis, is as uninvolving as the detached moniker suggests. It attempts to serve up deep truths about love and loss, but only manages to be precious and overheated. It's hard to imagine it provoking the same passionate debates as the Oscar-winning “Crash,” which divided cinephiles with its depiction of racism in Los Angeles. Say what you will about that movie, at least it had vitality and interesting characters.