Moving Objects on Same Layer to Groups Changes Object Order

Objects on the same layer will have their order changed after moving them to a group. This only occurs when Shift-selecting the objects from bottom to top, or Ctrl-selecting the objects top to bottom.

Steps to reproduce:

1. Select the stamp tool and place 2 stamps, then group them

2. Place another clump of stamps with multiple stamps overlapping

3. In the object list, select the stamps with Shift-select (bottom to top), or Ctrl-select (top to bottom)

4. Move the selected stamps to the group

Expected: Stamps should keep their current order after moving to group.

Actual: Stamp order is changed after moving to group.