Fix template problems with gr-main-header

Change-Id: Id824b13f3fe065f3efd68df099f792919a9dafe8
diff --git a/polygerrit-ui/app/BUILD b/polygerrit-ui/app/BUILD
index 20d66a5..1f4cc4e 100644
--- a/polygerrit-ui/app/BUILD
+++ b/polygerrit-ui/app/BUILD
@@ -107,7 +107,6 @@
     "elements/change/gr-reviewer-list/gr-reviewer-list_html.ts",
     "elements/change/gr-thread-list/gr-thread-list_html.ts",
     "elements/checks/gr-hovercard-run_html.ts",
-    "elements/core/gr-main-header/gr-main-header_html.ts",
     "elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog_html.ts",
     "elements/diff/gr-diff-builder/gr-diff-builder-element_html.ts",
     "elements/diff/gr-diff-host/gr-diff-host_html.ts",
diff --git a/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts b/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
index f7e61bf..fd7e25e 100644
--- a/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
+++ b/polygerrit-ui/app/elements/core/gr-main-header/gr-main-header.ts
@@ -110,7 +110,7 @@
   }
 
   @property({type: String, notify: true})
-  searchQuery?: string;
+  searchQuery = '';
 
   @property({type: Boolean, reflectToAttribute: true})
   loggedIn?: boolean;