Safe guard search initialization

The search initialization errors on pages that don't have a search (e.g.
login, terms agreement page)

app/assets/javascripts/main.js

@@ -111,7 +111,9 @@ function deferredInitialisation() {
   initPersistentUserCallouts();
   initDefaultTrackers();
 
-  document.querySelector('#search').addEventListener(
+  const search = document.querySelector('#search');
+  if (search) {
+    search.addEventListener(
       'focus',
       () => {
         import(/* webpackChunkName: 'globalSearch' */ './search_autocomplete')
@@ -123,6 +125,7 @@ function deferredInitialisation() {
       },
       { once: true },
     );
+  }
 
   addSelectOnFocusBehaviour('.js-select-on-focus');