Behaviour of inplace for `copy_range` when range is empty.

[wence-]

In copying.copy_range we have an inplace=False/True argument.

If inplace is True, then the column is modified in place, if inplace is False, a new (copied) column is created and then modified. If the case that the range we are copying is empty, at present inplace=False still returns a new copy (even though copy_range is a no-op in this situation).

Should it be allowed that

copy_range(source, target, empty_range, inplace=False)

Can return target (rather than a copy of target)?

See discussion where this came p: #12075 (comment)