Fix sequence generator test. (#3546)

ludwig/features/text_feature.py

@@ -302,11 +302,12 @@ def update_metrics(
             decoded_targets, decoded_predictions = get_decoded_targets_and_predictions(targets, predictions, tokenizer)
         for metric_name, metric_fn in self._metric_functions.items():
             prediction_key = get_metric_tensor_input(metric_name)
-            if prediction_key == RESPONSE and tokenizer is not None:
-                # RESPONSE metrics cannot be computed if decoded texts are not provided.
-                # Decoded texts are only provided using the LLM model type.
-                if decoded_targets is not None and decoded_predictions is not None:
-                    metric_fn.update(decoded_predictions, decoded_targets)
+            if prediction_key == RESPONSE:
+                if tokenizer is not None:
+                    # RESPONSE metrics cannot be computed if decoded texts are not provided.
+                    # Decoded texts are only provided using the LLM model type.
+                    if decoded_targets is not None and decoded_predictions is not None:
+                        metric_fn.update(decoded_predictions, decoded_targets)
             else:
                 metric_fn = metric_fn.to(predictions[prediction_key].device)
                 metric_fn.update(predictions[prediction_key].detach(), targets)