How do I perform Galois field multiplication?

I am using AES encryption. During mix / inverse mix column operations, I need to multiply the Galois field. I am using reference tables in the following document (section 5.4.2) https://www.ime.usp.br/~rt/cranalysis/AESSimplified.pdf

If you go to the section above, column (0,0) in table L is empty. So what can I get back when I say I need to search for L (0,0). I tried to return 0, but that gave me the wrong encryption.