diff --git a/examples/workflow_by_code/main.py b/examples/workflow_by_code/main.py
index 107146f..3534aae 100644
--- a/examples/workflow_by_code/main.py
+++ b/examples/workflow_by_code/main.py
@@ -18,7 +18,7 @@ from learnware.utils import get_module_by_module_path
 curr_root = os.path.dirname(os.path.abspath(__file__))
 
 user_semantic = {
-    "Data": {"Values": ["Tabular"], "Type": "Class"},
+    "Data": {"Values": ["Table"], "Type": "Class"},
     "Task": {
         "Values": ["Classification"],
         "Type": "Class",
diff --git a/learnware/market/easy.py b/learnware/market/easy.py
index 8c2d20a..bf551b5 100644
--- a/learnware/market/easy.py
+++ b/learnware/market/easy.py
@@ -203,6 +203,9 @@ class EasyMarket(BaseMarket):
                 pass
             return None, self.INVALID_LEARNWARE
 
+        if new_learnware is None:
+            return None, self.INVALID_LEARNWARE
+
         check_flag = self.check_learnware(new_learnware)
 
         add_learnware_to_db(