wordlist iterator should check for type and not just existence

[evilsocket]

In order to determine if a --username or --password argument value is a wordlist file, filepath.exists() is used. However, this will return true if the value is a folder, in which case BufReader.lines will result in an infinite loop. Type should be checked (is_file) other than just existence.

[evilsocket]

root cause of https://twitter.com/MikeWeinerRules/status/1721954308814463294