search: defensive programming

When the search failed fatally for some reason, returning `null` instead
of an empty-sized array of results, let's still tell the person viewing
the search results that none could be found.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

assets/js/application.js

@@ -284,8 +284,7 @@ var Search = {
         $("#search-term").text(term);
         this.initializeSearchIndex(async () => {
           const results = await Search.pagefind.debouncedSearch(term);
-          if (results === null) return;
-          if (results.results.length === 0) {
+          if (results === null || results.results.length === 0) {
             $("#show-results-label").text("No matching pages found.");
             return;
           }