Update app.py

app.py

@@ -252,10 +252,7 @@ def run_entity_exploration():
         if attr.get("type") == "instance":
             st.write("Found instance:", node, "of class:", attr.get("class_type"))
 
-    selected_entity = None  # <-- 安全宣告，避免未定義錯誤
-
-    if entities:
-        selected_entity = st.selectbox("Select Entity", entities)
+    selected_entity = st.selectbox("Select Entity", entities) if entities else None
 
     if selected_entity:
         entity_info = ontology_manager.get_entity_info(selected_entity)
@@ -272,7 +269,7 @@ def run_entity_exploration():
             max_distance=max_distance,
             include_classes=True
         )
-    else:
+    elif not entities:
         st.warning("No entities found in the ontology.")
     
     if selected_entity: