"Erase Empty Subsets" does not respect projectors

[bsumirak]

Steps to reproduce
(1) Create a sphere in subset 1.
(2) Set a sphere projector on subset 1.
(3) Apply "Erase Empty subsets".

Result: Subset 0 is replaced by former subset 1 and the latter removed. Subset 0 has no projector information.
Expected Result: Subset 0 has the projector information of former subset 1.

[sreiter]

Somehow this issue was somewhat lost in time... I don't think it is fixed yet. So thanks for reporting!