Cannot draw tiles to scene: "Undo objects may not be null"

Undo objects may not be null.

UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

I'm trying to learn how to use tilemaps in unity and I can't draw tiles to my scene, I can't find any information online about this error so I don't know if it's related or not

EDIT: I never made a tilemap in my hierarchy! right click in the hierarchy, 2D object (for 2D projects...) and choose "tilemap", otherwise you're not drawing to anything.

sorry unity forums. ignore this simpleton. continue about your business.

 

thanks

 

thanks