Updating user via Import does not allow External ID to be nulled out

Issue Summary

When updating a Jira Align user via import, the External ID value can be changed, but cannot be cleared / nulled

Steps to Reproduce

1. Go to Admin > People
2. Search for user with a populated External ID
3. More Actions > Export
4. Open xls file in Excel, delete the "External ID" value and Save
5. More Actions > Import Users Records
6. Browse and select the modified xls, Import
7. Refresh user record from JA UI

Expected Results

External ID value should be cleared

Actual Results

External ID is unchanged

Workaround

• Delete External ID via UI
• Delete External ID via API (set value to null)