Improve password-rules.json error catching in CI

[erynofwales]

I landed a change recently to fix a small formatting error in the password-rules.json file. This caused an error in some of our scripts:

Parsing password rules for hetzner.com
minlength: 8; required: lower; required: upper; required: digit, required: [-^!$%/()=?+#.,;:~*@{}_&[]];
_passwordGenerationParametersDictionary@(execjs):959:41: TypeError: null is not an object (evaluating 'requirements["PasswordMinLength"]') (ExecJS::ProgramError)