Version: 2.82a (Linux 64-bit)
How to reproduce:
- Open the attached file and render a frame
- In the outlier, disable rendering either "Layer A" OR "Layer B" and render a frame again. No problems so far.
- Now disable rendering for both view layers and try to render.
The expected outcome is that the background scene will still be rendered and compositing will be performed, outputting an image containing neither of the view layers. Instead, the whole process is aborted and the user receives an error message. One workaround is to enable the view layer "View Layer", causing it to be rendered even though it is unused in the compositor, but this should not be necessary.
It makes sense to warn the user if all the view layers are disabled, but it doesn't make sense to abort the render when there could be many cases in which this is intentional.