By Tom Sunderland Luke Littler’s mum, Lisa, couldn’t resist responding to Ricardo Pietreczko after his on-stage spat with son Luke at the Belgian Open. Teenage sensation Littler, still just 17, defeated ‘Pikachu’ Pietreczko 7-3 in Wieze when the pair met in the semi-final on Sunday afternoon. But things got heated before the two exited the stage, with Pietreczko confronting Littler when the teen went to shake his hand. The German got in his face in an extremely tense moment. Pietreczko did not reveal what he had said to Littler but took to Instagram with a scathing message. Writing on his Inst…