The catapult spell description says:
Choose one object weighing 1 to 5 pounds within range that isn’t being worn or carried.
The description of Bigby's hand states that it is a Large object with no defined weight, but it doesn't fill the space it's in (I'm not sure if that means it's hovering or if it's ghostly).
Let's say I target Bigby's hand with catapult and launch the hand 90 feet towards some bad guys. Would it fail as a possible use for catapult, or would it shoot off as normal and hit the first thing in its path?