Fix keyerror

app.py

@@ -86,6 +86,7 @@ def training():
     
     dataset_clean = {}
     for i in range(n_examples):
+        dataset_clean[i] = {}
         dataset_clean[i]["text"] = normalize(train_data[i]["text"], lowercase=True, remove_stopwords=True)
         dataset_clean[i]["label"] = train_data[i]["label"]