SINGAPORE/SHANGHAI—China Evergrande’s electric car unit warned on Friday it faced an uncertain future unless it got a swift injection of cash, the clearest sign yet that the property developer’s liquidity crisis is worsening in other parts of its business. Evergrande owes $305 billion, has run short of cash and investors are worried a collapse could pose systemic risks to China’s financial system and reverberate around the world. The company missed a payment deadline on a dollar bond this week and its silence on the matter has left global investors wondering if they will have to swallow large losses when a 30-day grace period ends. China Evergrande New Energy Vehicle Group, meanwhile, said without a strategic investment or the sale of assets its ability to pay staff and suppliers and mass-produce vehicles would be hit. Evergrande’s silence on this week’s $83.5 million interest payment contrasts with its treatment of its domestic …