salsaflow-commit-msg: Skip empty line on Story-Id
salsaflow-commit-msg: Skip empty line on Story-Id

Do not append an empty line to the commit message in case the last line is the
Story-Id tag. This is a heristic that help to mess up the commit message less.

Change-Id: 56c045d6d2
Story-Id: SF-15

salsaflow/salsaflow,salsaflow/salsaflow