abdel-kader russell-boumzar granted bail in brisbane court on thursday .
the 17-year-old is accused of racially abusing train guard in brisbane .
footage of the teenager allegedly spitting on guard went viral .
russell-boumzar spent 69 days behind bars for a string of alleged offences .
magistrate told him to stay out of trouble when released on bail .
he will reappear in court on may 4 for charges relating to the train incident .