Fix template problems with gr-autocomplete

Change-Id: I281345495ee5bd4c05a6ec9af061c86742dd5ead
diff --git a/polygerrit-ui/app/BUILD b/polygerrit-ui/app/BUILD
index 680359cac..e3272e3 100644
--- a/polygerrit-ui/app/BUILD
+++ b/polygerrit-ui/app/BUILD
@@ -113,7 +113,6 @@
     "elements/gr-app-element_html.ts",
     "elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts",
     "elements/shared/gr-account-list/gr-account-list_html.ts",
-    "elements/shared/gr-autocomplete/gr-autocomplete_html.ts",
     "elements/shared/gr-comment-thread/gr-comment-thread_html.ts",
     "elements/shared/gr-comment/gr-comment_html.ts",
     "elements/shared/gr-dropdown-list/gr-dropdown-list_html.ts",
diff --git a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.ts b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.ts
index 9a7b18f..9f6afe6 100644
--- a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.ts
+++ b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.ts
@@ -175,7 +175,7 @@
   _suggestionEls = [];
 
   @property({type: Number})
-  _index?: number;
+  _index: number | null = null;
 
   @property({type: Boolean})
   _disableSuggestions = false;