bug#69809: 30.0.50; flymake: error in process sentinel

[Gerd Möllmann]

In master, I am sometimes getting errors like these:

  error in process sentinel: flymake--handle-report: Can’t find state for 
flymake-cc in ‘flymake--state’
  error in process sentinel: Can’t find state for flymake-cc in ‘flymake--state’
  error in process sentinel: flymake--handle-report: Can’t find state for 
flymake-cc in ‘flymake--state’
  error in process sentinel: Can’t find state for flymake-cc in ‘flymake--state’
  error in process sentinel: flymake--handle-report: Can’t find state for 
flymake-cc in ‘flymake--state’
  error in process sentinel: Can’t find state for flymake-cc in ‘flymake--state’

when working with C files.

I haven't configured anything for Flymake myself. I think Flymake gets
involved by using Eglot. The errors apparently don't prevent flymake
from working later on.

I have looked around in flymake docs and source, but I can't figure out
what's wrong.