Allow lat/longs for transmissions without demes
Allow lat/longs for transmissions without demes

This avoids a bug where the lat/longs of internal nodes had to also be set for tips (demes) which may not always be the case.

Co-authored-by: mapmeld <b189c626495368fa9e1ea2a03297251cabba5778@mapmeld.com>
nextstrain/auspice,nextstrain/auspice,nextstrain/auspice