Rangers are ‘dismayed’ after Old Firm rivals Celtic reneged on a ticket allocation agreement for derby clashes this season. Rangers and Celtic had agreed to the return of away supporters next season after away fans were locked out of the four Scottish Premiership Old Firm clashes last season. But that agreement is now set to be ripped up by Celtic, a decision which has sent Rangers scrambling ahead of the first derby clash of the season at Parkhead on 1st September. It’s a situation which comes during an awful week at Rangers, with the club’s unceremonious Champions League exit at the hands of…