New layer inconsistently does not create new layer

[frnsys]

Description
If I have a lower layer selected, and add a new layer, a new layer is not added. Instead what happens is the focus moves to the layer above, but a duplicate of the top-most layer is added to the layer list, pointing to the same layer (see video).

To Reproduce

1. Have multiple layers
2. Select a lower layer
3. Click "Add Layer"

Additional Info
Video:
https://github.com/user-attachments/assets/c1c9ba56-9c7e-4922-a686-3cf0b58e3ad4

Version
OpenSUSE Tumbleweed, Wayland (niri), Pinta 3.1.2

[cameronwhite]

I think this was the same issue that #2150 just fixed

[frnsys]

Great, thank you!