[BUG] stop_words

[baisechundu]

When i try to add some stop_words for model，i found parameter stop_sequences in “lightllm/server/sampling_params.py”.
There seems to be some issues with line 67：
“ if stop_str_ids is not None and len(stop_str_ids) >= 1: ”
">=" here should be modified to ">". Otherwise, it will get an empty list when the len(stop_str_ids) equal 1.