Fixes in worker schema

portal/rest/schemas.py

@@ -273,9 +273,9 @@ class WorkerSchema(BaseSchema, Schema):
     """Component Schema
     """
     name = fields.Str()
-    url = fields.Str()
-    tags = fields.Str()
-    portal_secret = fields.Str()
+    url = fields.Str(allow_none=True)
+    tags = fields.Str(allow_none=True)
+    portal_secret = fields.Str(allow_none=True)
     state = EnumField(WorkerState)