erp5_json_form: Empty data doesn't mean data is valid

* Case of required properties

bt5/erp5_json_form/ModuleComponentTemplateItem/portal_components/document.erp5.JSONForm.py

@@ -73,8 +73,6 @@ class JSONForm(JSONType, TextDocument):
     """
     Validate contained JSON with the Schema defined in the Portal Type.
     """
-    if not json_data:
-      return True
     defined_schema = json.loads(self.getTextContent() or "")
     try:
       jsonschema.validate(json_data, defined_schema, format_checker=jsonschema.FormatChecker())

bt5/erp5_json_form/TestTemplateItem/portal_components/test.erp5.testJSONForm.py

@@ -214,3 +214,32 @@ return json.dumps({
     except ValueError, e:
       self.assertEqual(error, json.loads(str(e)))
 
+  def test_empty_data_with_required_property(self):
+    """
+    """
+    schema = """{
+	"$schema": "https://json-schema.org/draft/2019-09/schema",
+  "$id": "my-schema.json",
+  "properties":{
+    "title": {
+      "type": "string"
+    }
+  },
+  "required": ["title"]
+}"""
+    data = {}
+    method = "test_ERP5Site_processSimpleStriingAsJSON"
+    after_method = self.createBasicScriptreturnJSONWithTimestamp()
+    self.fixJSONForm(method, schema, after_method)
+    self.tic()
+    self.assertRaises(ValueError, getattr(self.portal, method), data, list_error=True)
+    error = {
+      "my-schema.json": [[
+        'Validation Error', u"u'title' is a required property"
+      ]]
+    }
+    try:
+      getattr(self.portal, method)(data, list_error=True)
+      raise ValueError("No error raised during processing")
+    except ValueError, e:
+      self.assertEqual(error, json.loads(str(e)))