Do return an empty but not null labelRect if no labelText
Do return an empty but not null labelRect if no labelText

Placemark symbol also competes for room, so it's valid to separate
an empty label on a displayable Placemark from one that would overlap
with existing text.

BUG: 310242

tzapzoor/marble,tucnak/marble,AndreiDuma/marble,Earthwings/marble,oberluz/marble,utkuaydin/marble,tzapzoor/marble,tucnak/marble,David-Gil/marble-dev,utkuaydin/marble,oberluz/marble,David-Gil/marble-dev,quannt24/marble,rku/marble,adraghici/marble,probonopd/marble,tucnak/marble,Earthwings/marble,tucnak/marble,AndreiDuma/marble,tzapzoor/marble,David-Gil/marble-dev,tucnak/marble,oberluz/marble,probonopd/marble,utkuaydin/marble,David-Gil/marble-dev,utkuaydin/marble,rku/marble,Earthwings/marble,rku/marble,rku/marble,Earthwings/marble,quannt24/marble,utkuaydin/marble,Earthwings/marble,David-Gil/marble-dev,AndreiDuma/marble,quannt24/marble,adraghici/marble,rku/marble,oberluz/marble,adraghici/marble,AndreiDuma/marble,tzapzoor/marble,probonopd/marble,adraghici/marble,tzapzoor/marble,probonopd/marble,tucnak/marble,AndreiDuma/marble,tzapzoor/marble,David-Gil/marble-dev,adraghici/marble,adraghici/marble,AndreiDuma/marble,probonopd/marble,quannt24/marble,quannt24/marble,tzapzoor/marble,probonopd/marble,rku/marble,quannt24/marble,probonopd/marble,tzapzoor/marble,oberluz/marble,oberluz/marble,utkuaydin/marble,tucnak/marble,Earthwings/marble,quannt24/marble