nil pointer when getting blob

[unknwon]

// ci is *git.Commit
for _, e := range ci.ListEntries() {
if e.IsDir() || strings.HasPrefix(e.Name(), ".") {
continue
}
rc, err := e.Blob().Data()
// e.Blob().Data() will deference a nil pointer, while e.Blob() is okay.
}

This is caused by this PR #8.