[trainer] fix vlm loss for transformers 4.49 (#7448)

src/llamafactory/train/pt/trainer.py

@@ -70,3 +70,7 @@ class CustomTrainer(Trainer):
             return torch.utils.data.SequentialSampler(self.train_dataset)
 
         return super()._get_train_sampler()
+
+    @override
+    def compute_loss(self, model, inputs, *args, **kwargs):
+        return super().compute_loss(model, inputs, *args, **kwargs)