fix: fix index out of bounds error in spec decoding#5954

lfr-0531 merged 2 commits intoNVIDIA:release/0.21NVIDIA/TensorRT-LLM:release/0.21from

lfr-0531:user/fanrongl/fix_spec_dec_indexlfr-0531/TensorRT-LLM:user/fanrongl/fix_spec_dec_indexCopy head branch name to clipboard