git: openjdk/skara: Fix webrev generation when target hunk is empty

[duke]

Changeset: c730de2b
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-08-26 09:29:27 +0000
URL:       https://github.com/openjdk/skara/commit/c730de2b

Fix webrev generation when target hunk is empty

Reviewed-by: rwestberg

! webrev/src/main/java/org/openjdk/skara/webrev/FramesView.java
! webrev/src/main/java/org/openjdk/skara/webrev/HunkCoalescer.java
! webrev/src/test/java/org/openjdk/skara/webrev/WebrevTests.java