Accessing global set's field gives object that couldn't be converted to string
Well, when I went properly through the output of {{ dump(company.businessName) }} I found out right from the start that it is element criteria model of entry type.
That led me to check for the handle company that could exists twice in system.

I found section with the handle company. So two identical handles in system were causing my problem. But on the first place, how could Craft let me save the global set with the handle that already existed in system even if they are different type of element criteria model and Craft would throw that string conversion error anyway?