Do not create label if string is empty.

Do not create a text label if the returned string is empty.
Also, fixed a potential crash after not creating a label and adding it to
the list of created labels.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Use the same behavior as the old time markers

This commit adds the same behavior for the old time markers on the new
ones.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix an issue added in the last commit

The last commit made the time and all other axis behave like the time
axis. Not cool.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>