add 1 to cur_len to make up the new beam length
# What does this PR do?
cur_len is 1 token shorter comparing to the length of the sequence whose best_sum_logprobs is the numerator.

Fixes # (issue)
add 1 to cur_len

## Who can review?
@LysandreJik 


_The documentation is not available anymore as the PR was closed or merged._<|||||>cc @gante<|||||>@gante Thx for the great advice. You are suggesting a better coding style. 