In my opinion IRS doesn't want anything listed there, for royalty income.  But I usually enter the states or countries where the wells/mines are located.  Why would IRS want the name of the payor?  They already have that, at least on domestic 1099 issuers.  

If leaving it blank causes a software error notification, ignore it.  

Line 1a
For rental real estate property only,
show the street address, city or town,
state, and ZIP code. If the property is located

in a foreign country, enter the city,
province or state, country, and postal
code.