steps to reproduce:
1. start with an empty database
2. create a configuration and generate two builds
3. switch to statitics page and select duration tab
4. select graph by version, and compare two metrics
5. select "success rate" for both metrics
A NPE will occur
Description
steps to reproduce:
1. start with an empty database
2. create a configuration and generate two builds
3. switch to statitics page and select duration tab
4. select graph by version, and compare two metrics
5. select "success rate" for both metrics
A NPE will occur