If a movie franchise has nothing especially new to say about itself or its mythology, perhaps it’s best if it refrains from trying to say anything at all. Such is the case with this latest installment in the “Tron” series of would-be sci-fi screen epics, a nondescript, underwhelming effort that, regrettably, disappoints in myriad ways. What starts out as a generally unengaging tale about AI corporate espionage that straddles life in the real world and cyberspace improves somewhat as it moves along, particularly in the back half when the connection to the original 1982 release becomes more apparent (and more compelling). But what precedes that development is uninspiring, even if it is visually dazzling to look at.