Fix reviewer autocomplete when NoteDB is not enabled

In gr-reply-dialog, _filterReviewerSuggestion expects _ccs to be
an array. Ensure it is one if NoteDB is not enabled.

Change-Id: I5fc5a181f64369e3c94ed599cd0a1b4289e24b1e
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
index 5b6bf16..b5cef75 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
@@ -329,6 +329,7 @@
       if (this.serverConfig.note_db_enabled) {
         this._ccs = ccs;
       } else {
+        this._ccs = [];
         reviewers = reviewers.concat(ccs);
       }
       this._reviewers = reviewers;