stringify document value if type in schema changed from object to string

jsonform/gadget_json_generated_form_child.js

@@ -685,6 +685,9 @@
       } else {
         input = document.createElement("input");
         if (default_value !== undefined) {
+          if (["object", "array"].indexOf(getDocumentType(default_value)) >= 0) {
+            default_value = JSON.stringify(default_value);
+          }
           input.value = default_value;
         }