[fix]修复单测test_encoder_decoder_model_runner报错问题

vllm/worker/model_runner.py

@@ -855,11 +855,12 @@ class ModelInputForGPUBuilder(ModelRunnerInputBuilderBase[ModelInputForGPU]):
         tree_attention_masks_list = []
         for inter_data in self.inter_data_list:
             for i in range(len(inter_data.seq_lens)):
+                if inter_data.tree_attn_masks:
                     tree_attn_masks = inter_data.tree_attn_masks[i]
                     if tree_attn_masks is not None:
                         tree_attention_masks_list.append(tree_attn_masks)
         tree_attention_masks_tensor = None
-        if len(tree_attention_masks_list) > 0:
+        if tree_attention_masks_list:
             tree_attention_masks_tensor = torch.stack(tree_attention_masks_list, dim=0)
             tree_attention_masks_tensor = tree_attention_masks_tensor.contiguous()