By Ryan Merrifield The heartbroken aunt of an eight-year-old boy mowed down by a speeding thug said he was “too good for this cruel world”. Mustafa Ahmed was on a pedestrian crossing with his dad and brother outside Greenwich Islamic Centre in Plumstead, East London, when he was struck by unlicensed and uninsured Nicholas Hopkins’s motorbike. The 20-year-old killer – who grinned in his mugshot after being arrested \- was on bail after threatening his ex-girlfriend with a pair of scissors, before assaulting and strangling her. He was today jailed for 12 years at Inner London Crown Court. Little…