[Bug] Robot cannot recover from a failed plan

[Spydrouge]

Ordinarily this might not be obvious, because if the robot formed a bad plan to get to a battery and became stumped, he obviously could move no farther than he already has (as he would just keep coming up with new plans, and all of those new plans would be identical to his old plan)

But, for example, if a robot attempts to eat a battery, and I delete the battery before he arrives, the planner will continuously report 'failed' and the robot will try no alternative plans of any kind- even if new batteries appear all over the place.