Private equity giant Blackstone Group has called off the sale of its A$3.5 billion ($2.8 billion) Australian shopping mall portfolio, a source said, as the looming arrival of Amazon spooks buyers of bricks-and-mortar stores. With no interest in the entire 10-mall package, the canceled sale is also the latest sign of stress in Australia's east-coast real estate market, where population growth and booming property prices have underpinned landlords' profits for years.