Are you making a joke, or are you not familiar with multicopters?
If one motor dies or its prop breaks or something, the computer detects that and turns that motor off, and the motor on the opposite side of the craft (which will be spinning in the opposite direction.) This will keep the forces balanced.
Then you speed up the remaining motors to make up for the lost lift. Given that you've only lost/turned off 25% of your motors, the thing would almost certainly still be able to maneuver normally. Performance would be reduced, yes -- but it would be designed to be able to lose some number of its motors and still maintain altitude and fly around.
And even if you were to lose all four bottom motors/props -- even if that doesn't leave it with enough power to maintain altitude (which is uncertain -- it might still be able to fly with only four motors), it would still be able to make a controlled descent at a reasonable rate of speed. (It might not be able to pick its landing spot, however.)
That said, given that human life would be on the line here -- I'd expect these things to also be equipped with a ballistic parachute. You probably wouldn't need it if one motor or prop failed, but if more things went south (or the computer or power source failed) -- you might.