I was creating a feature class by importing fields from another layer.
I was in editing and I forgot to save. I was not working on the layer I used to import though. Anyway, I got this error.
The problem now is that I cannot close this error and save the edits as this message keeps on reopening in a loop.
Happened again once, I solved by closing the project.
Can it be a bug? (ArcGIS PRO 2.2.4)