Bug fix for undefined "suggestion.tag_name"

scripts/top_nav.js

@@ -13,7 +13,7 @@ autocomplete('#search-input', { hint: false }, [
                     resultHeading = suggestion.title;
                 }
                 else {
-                    if (suggestion.tag_name[0] !== 'h') {
+                    if ((!suggestion.tag_name) || suggestion.tag_name[0] !== 'h') {
                         // If the suggestion did not match a heading, then we can use the heading
                         // from the hierarchy
                         if (suggestion.hierarchy) {

scripts/top_nav.ts

@@ -21,7 +21,7 @@ autocomplete('#search-input', { hint: false }, [
         } else if (suggestion.title) {
           resultHeading = suggestion.title;
         } else {
-          if (suggestion.tag_name[0] !== 'h') {
+          if ((!suggestion.tag_name) || suggestion.tag_name[0] !== 'h') {
             // If the suggestion did not match a heading, then we can use the heading
             // from the hierarchy
             if (suggestion.hierarchy) {