Adapt suggestReviewers to new method signature

Call suggestReviewers with null change notes to get per-project
suggestions.

Change-Id: Ie40d0068ad5e01f66cff0699d9a7f2e1bbef470a
diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewers/SuggestProjectReviewers.java b/src/main/java/com/googlesource/gerrit/plugins/reviewers/SuggestProjectReviewers.java
index b583a62..40c88f7 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewers/SuggestProjectReviewers.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewers/SuggestProjectReviewers.java
@@ -50,7 +50,7 @@
   @Override
   public List<SuggestedReviewerInfo> apply(ProjectResource rsrc)
       throws BadRequestException, OrmException, IOException {
-    return reviewersUtil.suggestReviewers(this, rsrc.getControl(),
+    return reviewersUtil.suggestReviewers(null, this, rsrc.getControl(),
         getVisibility(rsrc), true);
   }