Length of hist_item_seq[batch_size][i] error

The condition that max length of hist_item_seq[batch_size][i] == 1 is not covered. But it is happened when I run the baseline of dien model.

models/rank/dien/model.py

@@ -229,6 +229,10 @@ class Model(ModelBase):
         neg_seq_pad, _ = fluid.layers.sequence_pad(neg_reshape_hist_item_emb,
                                                    pad_value)
         seq_shape = fluid.layers.shape(pos_seq_pad)
+        
+        if(seq_shape[1] < 2):
+            aux_loss = 0
+        else:
             test_pos = fluid.layers.reduce_sum(
             fluid.layers.reduce_sum(
                 fluid.layers.log(