Any hopes you may have harbored of seeing Hamill stage a Star Wars-size come-back will be dashed once you sit through the tepid, boy-who-cried-U.F.O. mishmash Laserhawk, about a high school prankster who discovers that aliens are planing to eat yes, eat humanity. An after-school special with Battlestar Galactica-quality F/X, Laserhawk only serves to remind that the ''sci-fi for teens'' genre is one big black hole. C-

