return empty array [] only after user change array

jsonform/gadget_json_generated_form_child.js

@@ -601,16 +601,22 @@
   function render_array(gadget, schema, json_document, div_input, path, schema_path) {
     var input,
       minItems = schema.minItems || 0;
+    if (schema.default === undefined &&
+        json_document === undefined) {
+      div_input.setAttribute("data-undefined", "true");
+    }
 
     function element_append(child) {
       if (child) {
         input.parentNode.insertBefore(child, input);
+        div_input.removeAttribute("data-undefined");
       }
     }
 
     function div_append(child) {
       if (child) {
         div_input.appendChild(child);
+        div_input.removeAttribute("data-undefined");
       }
     }
 
@@ -1370,7 +1376,8 @@
         array = options.arrays[path]
           .querySelectorAll("div[data-gadget-parent-scope='" + g.element.getAttribute("data-gadget-scope") + "']");
         len = array.length;
-        if (len === 0) {
+        if (len === 0 &&
+            !options.arrays[path].hasAttribute('data-undefined')) {
           convertOnMultiLevel(multi_level_dict, path.slice(0, -1), []);
         }
         for (i = 0; i < len; i = i + 1) {