ZeroDivisionError

```
Reading: 100.00 %Traceback (most recent call last):
  File "./monkeytest.py", line 193, in <module>
    main()
  File "./monkeytest.py", line 189, in main
    benchmark.print_result()
  File "./monkeytest.py", line 165, in print_result
    max=self.read_block_b / (1024 * 1024 * min(self.read_results)),
ZeroDivisionError: float division by zero
```