Version prediction is not shown for sample data

Steps to reproduce:

1. Board has working days Mon-Fri
2. Today is Friday
3. Create sample scrum board
4. Version 3.0 has 2 issues, both 5 points. Mark one of them as done.
5. View the Version Report.

Adding Saturday as a working day makes the prediction happen correctly.

Debugging through the code, it seems that the "estimate per day" is calculated as 0.