Thanks to CNN I now know the “a” at the end makes it non-racist.
Via Mediaite:
… Jeantel explained to Morgan that “the whole world say it’s a racist word” but the version of the word that she testified Martin had used in reference to Zimmerman, spelled “n-i-g-g-a” doesn’t mean what most people think it means. It doesn’t mean a “black male” as Morgan assumed, she said, but rather any kind of man, including “Chinese” for example. Morgan helpfully pointed out that that’s the version rappers use in their music.
“But nigger,” Jeantel said, stressing the “-er.,” is a “racist word.” She said “I’d advise you not to be by black people” when you say that word, Jeantel explained, “because they’re not going to have it like that.” And this is not just in her community as Morgan posited but in the entire “generation.”