InputfieldMapMarker::isEmpty() issue

[Toutouwai]

When determining if the inputfield is empty or not (to determine visibility depending on the setting) the test says that if the lat value === 0.0 then the inputfield is empty.

But the test should be comparing against whatever the default lat for the field is as defined in the field settings (which probably won't be 0.0). If the inputfield lat value matches the default lat value then the field should be considered empty.