If loader is null, the script engine factories that are bundled with the platform and that are in the usual extension directories (installed extensions) are loaded

Author: Sasha Romanyshyn

handlebars/src/main/java/com/github/jknack/handlebars/Handlebars.java

@@ -1456,7 +1456,7 @@ private ScriptEngine engine() {
     synchronized (this) {
       if (this.engine == null) {
 
-        this.engine = new ScriptEngineManager().getEngineByName("nashorn");
+        this.engine = new ScriptEngineManager(null).getEngineByName("nashorn");
 
         Throwing.run(() -> engine.eval(Files.read(this.handlebarsJsFile, charset)));
       }