The highest court in Massachusetts upheld the dismissal of a second-degree murder indictment against a Lynn teenager accused of fatally stabbing another teenager during a drug robbery. On Wednesday, the Supreme Judicial Court affirmed a decision by a Superior Court judge to throw out the indictment against Javon Walczak. Authorities alleged that Walczak fatally stabbed Rene Valdez of Medford in August 2010. Both were 16. Police said Valdez and another teenager had previously bought marijuana from Walczak and arranged to meet him with the intention of robbing him. The lower court judge found that Valdez and the other teenager were the aggressors and that Walczak reacted in self-defense.