Add missing clone.

src/object.c

@@ -525,7 +525,7 @@ void _copyList(Object* dest, const Object* src)
         } else if (isStringy(*POINTER)) {
             nf_addToList(dest, cloneString(*POINTER));
         } else {
-            nf_addToList(dest, *POINTER);
+            nf_addToList(dest, cloneObject(*POINTER));
         }
     }
 }