Blender Git Loki

Fix T57558: Outliner displaying same object twice in some cases.

Logical flaw in `BKE_scene_objects_iterator_begin()` code (two errors
actually, wrong handling of first object of Master collection, and
missing call to `object_base_unique()` to 'register' that first object
and avoid getting it returned a second time).

Simply fixed by always calling `BKE_scene_objects_iterator_next()`
after minimal proper init, that one knows how to do the things. ;)