Revert "Save latitude and longitude on XML even if location not set"

This fixes the bug in #440 by accident, and introduces lots of empty
attributes and tags in the xml.

This reverts commit 6378bfd91ee6c0ad746b072d8a9389e0eba7c614.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Terminate the string before relying on strlen

Its a c-string we put, so it must be null-terminated.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Qt turns edited locations into null-strings

They aren't null pointers after you touched them, so we can't rely on
that to choose if we should use put_string or show_utf8.
show_utf8 would not print the tag if it only contains a \0 as body.

Fixes #440

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>