fix: handle None values in build_system_context and improve favicon response

llm.py

@@ -45,6 +45,12 @@ def build_system_context(
     whatif: dict,
 ) -> str:
     """Build structured context string from student analysis data."""
+    
+    # Guard against None values
+    student_data = student_data or {}
+    prediction = prediction or {}
+    explanation = explanation or {}
+    whatif = whatif or {}
 
     # ── Student Profile ──
     student_lines = [

main.py

@@ -506,7 +506,11 @@ async def read_index():
 # 3. Handle favicon if needed
 @app.get("/favicon.ico", include_in_schema=False)
 async def favicon():
-    return FileResponse("favicon.ico")
+    # Return 204 No Content if favicon doesn't exist to avoid 500 errors
+    if os.path.exists("favicon.ico"):
+        return FileResponse("favicon.ico")
+    from fastapi.responses import Response
+    return Response(status_code=204)
 
 if __name__ == "__main__":
     import uvicorn

script.js

@@ -1128,7 +1128,7 @@ async function initializeChat() {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
             body: JSON.stringify({
-                student_data: formData,
+                patient_data: formData,
                 prediction: currentPrediction,
                 explanation: currentExplanation,
                 whatif: currentWhatIf || {}