Merge 'stable-3.4' into master

* branch 'stable-3.4':
  Don't call 'review' with empty ReviewInput

Change-Id: I7c37f5016185823958478227b7cfce1316a604ef

src/main/java/com/googlesource/gerrit/plugins/reviewers/AddReviewers.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewers/AddReviewers.java b/src/main/java/com/googlesource/gerrit/plugins/reviewers/AddReviewers.java
index 5375481..099db37 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewers/AddReviewers.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewers/AddReviewers.java
@@ -88,6 +88,9 @@
               .filter(c -> !existingReviewers.contains(c))
               .filter(r -> !reviewersToAdd.contains(r))
               .collect(Collectors.toSet());
+      if (reviewersToAdd.isEmpty() && ccsToAdd.isEmpty()) {
+        return;
+      }
 
       ReviewInput in = new ReviewInput();
       in.reviewers = new ArrayList<>(reviewers.size() + ccs.size());