Add thisObj validation to prevent NullPointerException on non-object this values

Author: anivar

rhino/src/main/java/org/mozilla/javascript/NativeES2025Iterator.java

@@ -132,8 +132,11 @@ private static Object js_concat(
         return new ConcatIterator(cx, scope, iterables, iteratorMethods);
     }
 
-    private static Callable getNextMethod(Scriptable iterator) {
-        Object next = ScriptableObject.getProperty(iterator, "next");
+    private static Callable getNextMethod(Object thisObj) {
+        if (thisObj == null || !(thisObj instanceof Scriptable)) {
+            throw ScriptRuntime.typeError("Iterator method called on non-object");
+        }
+        Object next = ScriptableObject.getProperty((Scriptable) thisObj, "next");
         if (!(next instanceof Callable)) {
             throw ScriptRuntime.typeError("Iterator must have a next method");
         }