Fix bug in the MessageOfTheDayBar class

What steps will reproduce the problem?
- Add 2 or more message of the day.
- Dismiss them.
- Add one more or more.

What is the expected output?
Added (not dismissed) messages.

What do you see instead?
All (include dismissed) messages.

Bug: Issue 5049
Change-Id: Idd12d1940b2fc9abc6861f8facc3c0af34aa6ccc

gerrit-gwtui/src/main/java/com/google/gerrit/client/MessageOfTheDayBar.java

@@ -46,10 +46,10 @@ class MessageOfTheDayBar extends Composite {
     initWidget(uiBinder.createAndBindUi(this));
 
     SafeHtmlBuilder b = new SafeHtmlBuilder();
-    if (motd.size() == 1) {
-      b.append(SafeHtml.asis(motd.get(0).html));
+    if (this.motd.size() == 1) {
+      b.append(SafeHtml.asis(this.motd.get(0).html));
     } else {
-      for (HostPageData.Message m : motd) {
+      for (HostPageData.Message m : this.motd) {
         b.openDiv();
         b.append(SafeHtml.asis(m.html));
         b.openElement("hr");