Help with making a company shop in a city it was not in

[Reaper42]

I have made a edit of one of the prefabs for wallbert/Sellgoods. Then I put it in a city that did not have one. i have edited the files and it seems to show up in the game. I do get an error in the console that company item without company assignment for that building. How do I fix this error and how do I get the company to actually work?