components/calendar: Fix undefined string error
model.subLabel isn't always set, so we should return an empty string if it's not. This fixes the error: "DayDelegate.qml:205: Unable to assign [undefined] to QString"
cc @tantalising
model.subLabel isn't always set, so we should return an empty string if it's not. This fixes the error: "DayDelegate.qml:205: Unable to assign [undefined] to QString"
cc @tantalising