Set Tagger-Date to current time if empty or not present (as the docs say it should)

According to the docs:

If Committer-Date or Tagger-Date fields are not present they are filled in with the time at which this command is executed.

However, when creating a new tag without a Tagger-Date

msgin --create <<EOF
Tag-Name: test-tag
Tagger: Foo Bar <foo@bar.baz>

This is an example new tag.
EOF

the resulting tag would receive a date of 1970-01-01 (according to git show test-tag).

It seems like the current code does not assign any date to the tag (resulting in a "0" unix timestamp) when the condition taggerdate != "" was not met.