Objects with zero rows will not be downloaded. This also means that no tables will be created for empty objects. You can see the list of empty objects with:
select * from sfm.sfm_objects where is_queryable = 1 and cant_query = 0 and is_empty = 1
When rows are added to an empty object the is_empty flag will be removed on the next download. If the object is set to be downloaded tables will be created for it and all data will be downloaded automatically.