fix parameterless run

[changbowen]

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Commit f0f6f3d breaks the possibility to run the script without parameters. Adding a default parameter set fixes it.

[teddybear082]

Thank you this fixed an error I encountered, and thank you big time to jtmoon79, for creating this script. I was bashing my head against the wall how to get a truly portable python environment running until I found this.

[jtmoon79]

Thanks @changbowen !