In fact, Tiangong-1 isn't even the largest satellite to make an uncontrolled descent. Skylab, the US's first space station, crashed in Western Australia without injuring anyone in 1979. NASA’s 12-ton Upper Atmosphere Research Satellite had an uncontrolled descent in 2011 and landed safely in the Pacific Ocean.
Tiangong is an eight-ton craft, about ten times smaller than Skylab.
It's very unlikely you're going to be hit by a piece of the satellite. "The personal probability of being hit by a piece of debris from the Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning," the ESA said in a statement. The odds of a piece hitting you are less than one in a trillion. You're far more likely to win the lottery.
"It’s really very, very, very tiny odds," Andrew Abraham, an analyst at the Aerospace Corporation, told the New York Times. "I certainly would worry about things like crossing the street far more than debris from Tiangong."