Update app.py

app.py

@@ -279,7 +279,7 @@ def prepare_data(df):
     from sklearn.model_selection import train_test_split
 
     # If no target column is specified, select the first object column or the last column
-    if target_column is None:
+    if target_column_global is None:
         raise ValueError("Target column not set.")
     
     X = df.drop(columns=[target_column_global])