git: openjdk/skara: Fix webrev generation issue when a source hunk is empty

[duke]

Changeset: 6f884423
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2019-08-16 13:34:34 +0000
URL:       https://git.openjdk.java.net/skara/commit/6f884423

Fix webrev generation issue when a source hunk is empty

Reviewed-by: ehelin

! webrev/build.gradle
! 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