git: openjdk/skara: GitCommitIterator should handle empty commits

[duke]

Changeset: c19224a9
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-08-19 08:03:45 +0000
URL:       https://git.openjdk.java.net/skara/commit/c19224a9

GitCommitIterator should handle empty commits

Reviewed-by: rwestberg

! vcs/src/main/java/org/openjdk/skara/vcs/git/GitCommitIterator.java
! vcs/src/test/java/org/openjdk/skara/vcs/RepositoryTests.java