* app/gimpdrawable.c (gimp_drawable_set_name): Fix adding of
  numbers after drawable copies. We used to get pairs of duplicates
  after adding the same name several times.

(Try by adding a new layer several times in the layers dialog. You will
get New Layer, New Layer#2, New Layer#3, New Layer#3 (again!), New Layer#4,
New Layer#4 (again!), etc.)