Sometimes index returns empty string instead zero value

Signed-off-by: Michael Granados <michaelgranados@gmail.com>
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Merge branch 'master' of github.com:phpDocumentor/phpDocumentor2
Merge branch 'develop' of github.com:phpDocumentor/phpDocumentor2 into develop
Merge pull request #1465 from dgmike/issue-1460

Sometimes index returns empty string instead zero value