Cleaned up empty try/except statements

Added an Exception to empty try/except statements. This has the benefit of try statements from catching exceptions they really shouldn't be catching (such as system exceptions or KeyboardInterruptException).

More information can be found under the "except:" section [here](http://docs.python.org/2/howto/doanddont.html)

Also fixed a tiny typo in the nmap scan error handling. :)