Safe guard exdoc:autocomplete-limit meta access (#2142)

Can be seen in a few places in browser console, f.ex. https://hexdocs.pm/phoenix/overview.html

Error:
Uncaught TypeError: can't access property "content", document.querySelector(...) is null

Author: weih-kahoot

assets/js/search-bar.js

@@ -62,7 +62,7 @@ export function focusSearchInput () {
 
 function setAutocompleteLimit () {
   const searchInput = qs(SEARCH_INPUT_SELECTOR)
-  const autocompleteLimit = parseInt(document.querySelector('meta[name="exdoc:autocomplete-limit"]').content)
+  const autocompleteLimit = parseInt(document.querySelector('meta[name="exdoc:autocomplete-limit"]')?.content)
   if (autocompleteLimit) {
     window.autocompleteLimit = autocompleteLimit
   }