[gnome-bootstrap-theme] fix: only execute code if search element exists

[Guillaume Bernard <gbernard src gnome org>]

commit c73fed45a4277da789b0dbf047e54b7f44f7b8c2
Author: Guillaume Bernard <associations guillaume-bernard fr>
Date:   Sun Sep 25 15:14:24 2022 +0200

    fix: only execute code if search element exists

 src/js/navbar-search-form.js | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
---
diff --git a/src/js/navbar-search-form.js b/src/js/navbar-search-form.js
index 2aab4e2..18a6619 100644
--- a/src/js/navbar-search-form.js
+++ b/src/js/navbar-search-form.js
@@ -1,7 +1,10 @@
 const searchbar = document.getElementById('.js-search');
-document.getElementById('.js-search-toggle').onclick = function () {
-    searchbar.parent.closest('div').classList.toggle('is-visible');
-    setTimeout(function () {
-        searchbar.focus()
-    }, 350)
-};
+const js_search_toggle = document.getElementById('.js-search-toggle')
+if (js_search_toggle) {
+    js_search_toggle.onclick = function () {
+        searchbar.parent.closest('div').classList.toggle('is-visible');
+        setTimeout(function () {
+            searchbar.focus()
+        }, 350)
+    };
+}
\ No newline at end of file