Hello! I got the problem as in the title of the topic.
“Assertion failed on expression: ‘gOnDemandAssets-> empty () || GetOnDemandModeV2 ()! = AssetDatabase :: OnDemandMode :: Off’”
Yesterday I tried to add analytics from google to my working project - Firebase core. When installing the latest version, many errors appeared in the console, I immediately deleted this asset, installed the older version of firebase. Everything now works fine, the project starts and compiles, but after any change in the code or start / stop of the project, this annoying line began to appear in the console every time. What should I do?
For the sake of experiment, I tried to delete the entire Library folder so that the project would recreate it on a new one … It did not help 
P.S. I did the installation and uninstallation through the Package Manager. Unity 2019 version 3.7f1
