Filter None text values to fix TypeError in join

train.py

@@ -40,7 +40,12 @@ print(f"Rows: {len(ds)}, Columns: {ds.column_names}")
 print("Grouping conversations...")
 conversations = defaultdict(list)
 for row in ds:
-    conversations[row["conversation_id"]].append(row)
+    text = row["text"] if row["text"] is not None else ""
+    conversations[row["conversation_id"]].append({
+        "speaker": row["speaker"],
+        "date_time": row["date_time"],
+        "text": text,
+    })
 
 for conv_id in conversations:
     conversations[conv_id].sort(key=lambda x: x["date_time"])
@@ -55,7 +60,6 @@ for conv_id, turns in conversations.items():
     for turn in turns:
         role = "user" if turn["speaker"] == "client" else "assistant"
         if role == current_role:
-            # Merge consecutive same-role turns
             current_content.append(turn["text"])
         else:
             if current_role is not None: