Fix template problems with gr-confirm-abandon-dialog

Change-Id: If1605384893560837d6ab524796f763cfdc76f67
diff --git a/polygerrit-ui/app/BUILD b/polygerrit-ui/app/BUILD
index dd74087..b3e29ba 100644
--- a/polygerrit-ui/app/BUILD
+++ b/polygerrit-ui/app/BUILD
@@ -113,7 +113,6 @@
     "elements/change/gr-change-metadata/gr-change-metadata_html.ts",
     "elements/change/gr-change-requirements/gr-change-requirements_html.ts",
     "elements/change/gr-change-view/gr-change-view_html.ts",
-    "elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog_html.ts",
     "elements/change/gr-file-list-header/gr-file-list-header_html.ts",
     "elements/change/gr-file-list/gr-file-list_html.ts",
     "elements/change/gr-label-score-row/gr-label-score-row_html.ts",
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
index 04326a6..26e2fb4 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
@@ -1094,7 +1094,7 @@
         );
         tap(abandonButton);
 
-        assert.isUndefined(element.$.confirmAbandonDialog.message);
+        assert.equal(element.$.confirmAbandonDialog.message, '');
       });
 
       test('works', () => {
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.ts
index 4fd42b0..07da53f 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-abandon-dialog/gr-confirm-abandon-dialog.ts
@@ -57,7 +57,7 @@
    */
 
   @property({type: String})
-  message?: string;
+  message = '';
 
   get keyBindings() {
     return {