Manager Mark Bonner has insisted that returning Gillingham midfielder Bradley Dack is back for the right reasons. The Gills landed a transfer coup on Thursday by luring 30-year-old Dack back to Priestfield after spells in the Championship with Blackburn and Sunderland. After struggling with injuries in recent years, Dack isn’t here just to see out his career according to the Gills boss. “There’s a few boxes to tick,” stressed Bonner. “There’s the physical one of what can we get out of him, how can we get him going, how fit can we get him and how many games can we get him available for? “The se…