Fix bug when a project has no violation

When you use the `--fail-condition` parameter of the `analysis` command and the project has no violation the following bug occurs:
```
php insight.phar analysis 87ec89e6-57cd-4ac0-9ab1-d4549c5425c5 --fail-condition="analysis.getGrade() != 'platinum'"

The project has 0 violations, it got the platinum grade.

Re-run this command with -v option to get the full report
PHP Warning:  Invalid argument supplied for foreach() in phar:///var/lib/jenkins/insight.phar/SensioLabs/Insight/Cli/Command/AnalysisCommand.php on line 60
jenkins
```

This PR fixes it.