Running Nexus 1.3.4 with Krastorio2-spaced-out 2.0.0 (Factorio 2.0.77, Space Age)
logs this sprite error during atlas building:

Error AtlasBuilder.cpp:1266: File
__Krastorio2Assets__/buildings/antimatter-reactor/antimatter-reactor-light.png
not found; ...
  Prototypes using the sprite:
    data.raw["burner-generator"]["kr-antimatter-reactor"]

Cause: Nexus (compatibility/Krastorio2-spaced-out/entity_update.lua) redefines
the kr-antimatter-reactor burner-generator, and the first layer of its animation
is:

    filename = "__Krastorio2Assets__/buildings/antimatter-reactor/antimatter-reactor-light.png",
    priority = "high",
    width = 660, height = 706,
    frame_count = 1, repeat_count = 30,
    draw_as_light = true, blend_mode = "additive",

Krastorio2Assets 2.0.5 no longer ships antimatter-reactor-light.png. That folder
now contains only:
antimatter-reactor.png, antimatter-reactor-anim.png,
antimatter-reactor-glow.png, antimatter-reactor-sh.png

Suggested fix: drop that draw_as_light layer -- it's redundant with the -glow.png
layer that immediately follows it in the same animation -- or repoint it at an
asset that still exists.

Workaround for now: a tiny local mod that runs in data-final-fixes after Nexus
and removes the layer whose filename references antimatter-reactor-light.png from
data.raw["burner-generator"]["kr-antimatter-reactor"].animation.layers.

Environment: Factorio 2.0.77 (Space Age), macOS; Nexus 1.3.4,
Krastorio2-spaced-out 2.0.0, Krastorio2 2.0.19, Krastorio2Assets 2.0.5.