When Vincent F. Cornelius welcomes students from Northern Illinois University College of Law to the school’s 12th annual minority reception Wednesday, he will be giving them an opportunity he did not have when he earned his J.D. at NIU in 1989. “I had a sense that the minority alums — and particularly, at that time, African-American alums — were not really connected to one another, and to the law school, for that matter,” Cornelius said. “I thought that we were foregoing an …