'CSI' Star Marg Helgenberger -- I'd STILL Work with Bieber ... Despite His Bratty Cameo

"CSI" star Marg Helgenberger would be HONORED to work with Justin Bieber again -- despite what she said last year ... that the singer was an intolerable "brat" behind the scenes of her TV show.In case you didn't know, Bieber acted in one of the…