RAPPER Akon says he leapt into the crowd at his concert last night to stop brawling fans who triggered havoc at his performance. .. As the HiSense Arena gig in Melbourne with fellow rapper T-Pain reached full steam, Akon claims he was forced to stop his concert, as rival gangs appeared to launch brutal attacks on each other in the crowd.Police have confirmed two security guards were among at least 18 people who needed medical treatment as a result of violence... Nine people we…