Bug: Export to Google Sheet fails when there are deactivated users

[stevenle]

Describe the bug

When the ACLs contain inactive/deactivated users, the "Export to Google Sheet" feature fails due to sharing errors. In the short term, when sharing fails, skip the step and continue creating the spreadsheet.

In the long-term, we may want to have some way to validate and clean up the ACLs, although I'm not sure if Google provides any APIs we can leverage for the check.