Update app.py

app.py

@@ -16,7 +16,9 @@ def convert_schedule(file_path, direction):
         header2 = raw.iloc[1, 1:].astype(object)
 
         # Decide which header row to use: prefer second if fully populated
-        if header2.notna().all() and not header2.str.startswith('Unnamed').any():
+        # FIX: Convert to string before using .str accessor and handle NaN values
+        header2_str = header2.fillna('').astype(str)
+        if header2.notna().all() and not header2_str.str.startswith('Unnamed').any():
             days = header2.tolist()
             data_start = 2
         else: