The Ex is so thinly imagined and clumsily executed that it barely qualifies as a movie. But as a collection of funny little character sketches, it’s not bad. Any credit, then, goes to the actors, including Zach Braff, as an aimless new dad who reluctantly takes a job with his father-in-law’s advertising firm, and especially Jason Bateman as Chip, a vindictive, wheelchair-bound coworker who sets his sights on Braff’s wife (Amanda Peet). The filmmakers pretty much plop Chip in the movie as a politically incorrect gag, but Bateman gives each line reading so many layers it hardly matters. As on “Arrested Development,” where he played one of television’s funniest straight men, Bateman goes for such subtle, stinging laughs that only the most perceptive viewers will notice them.