fix file not load

frontend/exploration.py

@@ -18,11 +18,8 @@ if uploaded_file is not None:
     st.session_state.data = pd.read_csv(uploaded_file)
     st.success("File loaded successfully!")
 
-if "data" not in st.session_state:
-    st.session_state.data = None
 
-
-if st.session_state.data is not None:
+if "data" in st.session_state:
     data = st.session_state.data
     st.write(data.head(10))
     st.write(data.tail(10))