train_baseline error:IndexError: index 0 is out of bounds for axis 0 with size 0

[fendouai]

Train Epoch 0 loss 63.578703 855.35 (sec) <<
Valid Epoch 0 loss 24.911499
P:0.920358 R:0.946347 F:0.933171

Traceback (most recent call last):
File "train_baseline.py", line 176, in
train()
File "train_baseline.py", line 118, in train
predict= model.predict_step(sess, input_x)
File "/home/bigdata/CWS_Dict/same-domain/models/BaselineModel.py", line 126, in predict_step
viterbi_sequence, _=crf.viterbi_decode(unary_score[:length],transition_param)
File "/usr/local/lib/python2.7/dist-packages/tensorflow/contrib/crf/python/ops/crf.py", line 299, in viterbi_decode
trellis[0] = score[0]
IndexError: index 0 is out of bounds for axis 0 with size 0