save default value = empty object and use it for getContent if object does not have properties

jsonform/gadget_json_generated_form_child.js

@@ -1104,6 +1104,7 @@
       //input.setAttribute("class", "slapos-parameter");
       div_input.appendChild(input);
     } else {
+      div.setAttribute("data-parent-scope", gadget.element.getAttribute("data-gadget-scope"));
       div.setAttribute("data-json-path", first_path + '/');
       div.setAttribute("data-json-type", type);
     }
@@ -1325,6 +1326,11 @@
       root.appendChild(child);
     }
 
+    if (JSON.stringify(schema.default) === '{}') {
+      // save default value as attribute only for empty values
+      root.parentElement.setAttribute("data-default-value", '{}');
+    }
+
     if (json_document === undefined) {
       if (schema.hasOwnProperty('default')) {
         json_document = schema.default;
@@ -1588,6 +1594,18 @@
         });
     }
 
+
+    // set empty object if default value require this
+    array = g.element
+      .querySelectorAll("div[data-parent-scope='" +
+                        g.element.getAttribute("data-gadget-scope") + "']");
+    for (i = 0; i < array.length; i += 1) {
+      path = array[i].getAttribute("data-json-path").slice(0, -1);
+      if (array[i].getAttribute("data-default-value") === "{}") {
+        convertOnMultiLevel(multi_level_dict, path, {});
+      }
+    }
+
     for (path in options.arrays) {
       if (options.arrays.hasOwnProperty(path)) {
         array = options.arrays[path]