Query cause be cordump: select ORTHOGONAL_BITMAP_UNION_COUNT( cast(null as bitmap)) from t;
bitmap count functions result is null when there are null values, which is not right:
Result of select bitmap_to_string(bitmap_or(to_bitmap(1), null)) should be 1 instead of null. This PR fix logic of bitmap_or and bitmap_or_count. Other count related funcitons should also be checked and fix, they will be fixed in another PR.
