Generate site AIP package using packager fails with an NPE if using the passwords=true option

[amgciadev]

Describe the bug
The Generate site AIP package operation using the packager tool fails with an NPE if using the passwords=true option and there are any ePerson without a password set.

To Reproduce
Steps to reproduce the behavior:

1. An eperson without a password must exist in the DB (this is a common scenario in cases where shibboleth login is used)
2. Run package command to generate a site package with the passwords=true option, e.g. [dspace]/bin/dspace -d -t AIP -o passwords=true -e [admin email] -i [handle_prefix]/0 [full-path-to-aip-package]

Expected behavior
The process finishes cleanly and does now add a password entry for eperson without one set