Excpetion case no robot file

[XbandoleroX]

Using robots.txt as payload
Traceback (most recent call last):
  File "cansina.py", line 215, in <module>
    print("Reaped %s entries" % (len(robots_content)))
TypeError: object of type 'NoneType' has no len()

[deibit]

Fixed in #13