8356276: JavaScript error in script.js after JDK-8348282

Reviewed-by: liach

Author: hns

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/markup/Head.java

@@ -352,7 +352,6 @@ private void addStylesheets(HtmlTree head) {
 
         if (syntaxHighlight) {
             addStylesheet(head, DocPaths.RESOURCE_FILES.resolve(DocPaths.HIGHLIGHT_CSS));
-            addScriptElement(head, DocPaths.HIGHLIGHT_JS);
         }
 
         for (DocPath path : localStylesheets) {
@@ -367,6 +366,9 @@ private void addStylesheet(HtmlTree head, DocPath stylesheet) {
     }
 
     private void addScripts(HtmlTree head) {
+        if (syntaxHighlight) {
+            addScriptElement(head, DocPaths.HIGHLIGHT_JS);
+        }
         if (addDefaultScript) {
             addScriptElement(head, DocPaths.SCRIPT_JS);
         }

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/resources/script.js.template

@@ -21,8 +21,12 @@ var activeTableTab = "active-table-tab";
 const linkIcon = "##REPLACE:doclet.Link_icon##";
 const linkToSection = "##REPLACE:doclet.Link_to_section##";
 
-if (hljs) {
-    hljs.highlightAll();
+if (typeof hljs !== "undefined") {
+    try {
+        hljs.highlightAll();
+    } catch (err) {
+        console.error(err)
+    }
 }
 
 function loadScripts(doc, tag) {