The outputs of the Render Layers node in the compositor in the startup
file are missing. That's because add-ons are disabled when loading the
startup file, so Cycles will not be registered by the time the node tree
of the compositor is loaded, and its passes will not exist.
To fix this, we mark the compositor node tree as needing an update after
loading the startup file.
Pull Request: https://projects.blender.org/blender/blender/pulls/125053
cf032d6893