Implement jurisdiction validation in Streamlit app. Added error handling to ensure a valid jurisdiction is selected before loading data, enhancing user experience and preventing potential issues during app usage.

src/streamlit_app.py

@@ -49,6 +49,12 @@ hf_api = get_hf_api()
 @st.cache_data
 def load_grading_template(jurisdiction):
     """Load grading template from Hugging Face Dataset for the specified jurisdiction"""
+    # Validate jurisdiction is set
+    if not jurisdiction or jurisdiction not in AVAILABLE_JURISDICTIONS:
+        st.error(f"❌ **Error**: Jurisdiction is not set or invalid. Please select a valid jurisdiction.")
+        st.error(f"Available jurisdictions: {', '.join(AVAILABLE_JURISDICTIONS)}")
+        st.stop()
+    
     try:
         file_path = hf_hub_download(
             repo_id=HF_DATASET_REPO,
@@ -700,6 +706,21 @@ elif st.session_state.logged_in:
     jurisdiction = st.session_state.jurisdiction
     current_index = st.session_state.current_index
     
+    # Safety check: ensure jurisdiction is set (handles case where user was logged in before jurisdiction feature was added)
+    if not jurisdiction or jurisdiction not in AVAILABLE_JURISDICTIONS:
+        st.error("❌ **Error**: Jurisdiction is not set. Please log out and log in again with a jurisdiction selected.")
+        if st.button("Logout"):
+            st.session_state.logged_in = False
+            st.session_state.username = None
+            st.session_state.jurisdiction = None
+            st.session_state.current_index = 0
+            st.session_state.show_guide = True
+            st.session_state.submitted_pairs = set()
+            st.session_state.original_selections = {}
+            st.session_state.has_unsaved_changes = {}
+            st.rerun()
+        st.stop()
+    
     # Load grading template for the selected jurisdiction
     df = load_grading_template(jurisdiction)