Sometimes, when a goblin steals your wood and burns it up, you get a giant red error message. It usually says something about entities being nil or table index being nil.
This is happening because the log is being destroyed and its old parent stockpiles are confused about how to handle it. We are looking for the root cause of the error, but in the meantime, you can safely close the dialog and continue with your game. It’s unsightly, I know, but it doesn’t change the world state.
Edit: If you click on a line of the red error box, you get a black error box with increased details about the red error.