_minAMSLAltitude is always zero

[remster]

Expected Behavior

Please tell us what should happen as detailed as possible.
TransectStyleComplexItem::minAMSLAltitude() should return minimal altitude seen in the survey

Current Behavior

Owing to how it's initialised:

        _minAMSLAltitude = 0;
        _maxAMSLAltitude = 0;
        for (const QList<CoordInfo_t>& transect: _transects) {
            for (const CoordInfo_t& coordInfo: transect) {
                _minAMSLAltitude = qMin(_minAMSLAltitude, coordInfo.coord.altitude());
                _maxAMSLAltitude = qMax(_maxAMSLAltitude, coordInfo.coord.altitude());
            }
        }

it's always zero