[{"values":[1,2]},{"values":[5,null]},{"values":[-5,null]},{"values":[null,null]}]

db.collection.aggregate([{$project:{values:{$filter:{input:"$values",as:"d",cond:{$ne:["$$d",null]}}}}},{$match:{"values":{$ne:[]}}},{"$sort":{"values":1}}])