What is the Mock Worklog generation ?
The Workload Report allows to aggregate Worklog and to show depending on the Aggregation criteria the following calculation :

• Time Spent = Sum of entries of Users on the specified period
• Cumulated = Sum of all entries of Users on all issues
• Estimated = Sum of all Initially Estimated Time
• Remaining Time : Sum of Remaining Estimated Time (entered or deduced)
• Required Time : Cumulated + Remaining Time
• Gap : Engaged - Planned

The Search of Worklog is not done per Issue for performance reason, but by direct access to Worklog, using the Author, Start and End Date as main criteria.
It means that for specified period, it is possible that an issue has no Worklog.

Since the "Estimated" and "Remaining Time" are Issue attributes and aggregation is done by Worklog, we have to inject the aggregation mechanism some Mock Worklogs ...

Mock Worklog is Worklog Object with no spent time. When it is injected in the aggregation mechanism, it is also rendering in the Report and it is possible to see Issue with the "Estimated" and "Remaining Time" even if there is no effective logged Work for the considered period.

The bug raised in this issue is about the consistency of the Mock Worklog ... A Worklog requires a minimal set of attributes like :

• Start Date : Issue Create Date
• Time Spent : 0
• Author : the Assignee (historical reason of JIRA 3.7) or if null the Project Lead.

When there was no Assignee, the Author stayed to Null and not the Project Lead.
It causes a NPE and the display of an empty Author node in the report.