Interpreter mode crashes out on empty line

[haunab-ornl]

Providing an empty line to the interpreter results in a crash:

 % pkpass
Welcome to PKPass (Public Key Based Password Manager) v2.7.8!
Type ? to list commands
pkpass>
Generic exception caught:
    IndexError: list index out of range

[ginsburgnm]

yeah, we could do something with the postcmd function like adding the to beginning of the function the following

        if len(line.split()) == 0:
            return Cmd.postcmd(self, stop, line)

but something strange happens when you do that, and it will fix the empty line enter problem, but it will repeat previous commands as well. this would take additional investigation

[carljbai]

207 has a possible fix that avoids the issue with repeating previous commands.

[seriousbusinessprofessional]

207 has a possible fix that avoids the issue with repeating previous commands.

Tested this and it appears to be fixed.