My gut reaction was to say the "Evasion" autosoft. But looking up the description it very clearly states that Evasion is used to avoid Sensor lock.
That being said, a Defense test is not normally a skill test. Since Autosofts are used in place of skills, it would seem like they shouldn't use an autosoft at all. I looked up the rules for defense tests with vehicles, which are on page 205 of the Core Rulebook.
Normally, drivers roll Reaction + Intuition (like they normally would), and it specifically states that drones roll Pilot + Autosoft [Handling]. It doesn't specify what Autosoft, but based on the fact that defending generally involves moving, I would err on the side of Maneuvering. All-in-all it seems like Drones are getting a pretty short-ended stick here. This is the only time I've seen a defense that by default has a limit.
If there weren't a rule in the book, I would have said Pilot + Handling. Basically using Handling as Reaction, and Pilot as Intuition. But that would be a houserule.