Handle no polygon case

src/MissionManager/CorridorScanComplexItem.cc

@@ -305,12 +305,15 @@ void CorridorScanComplexItem::_rebuildCorridorPolygon(void)
     QList<QGeoCoordinate> secondSideVertices = _corridorPolyline.offsetPolyline(-halfWidth);
 
     _surveyAreaPolygon.clear();
+
+    QList<QGeoCoordinate> rgCoord;
     foreach (const QGeoCoordinate& vertex, firstSideVertices) {
-        _surveyAreaPolygon.appendVertex(vertex);
+        rgCoord.append(vertex);
     }
     for (int i=secondSideVertices.count() - 1; i >= 0; i--) {
-        _surveyAreaPolygon.appendVertex(secondSideVertices[i]);
+        rgCoord.append(secondSideVertices[i]);
     }
+    _surveyAreaPolygon.appendVertices(rgCoord);
 }
 
 void CorridorScanComplexItem::_rebuildTransectsPhase1(void)