The docs for a person states for the gender member:

The gender of this person. Either "Male", "Female" or "unknown", "n/a" if the person does not have a gender.

"Male" and "Female" are incorrect values; it should be "male" and "female".

Jabba's gender is "hermaphrodite" (though according to canon, Hutts now have a single sex and Jabba is male)

IG-88's gender is "none" - this should be "n/a"