Fixed a bug where a black line would be rendered when starting to draw a polygon.

src/FlightMap/FlightMap.qml

@@ -367,10 +367,12 @@ Map {
                 // Update drag coordinate
                 var polygonPath = polygonDrawerPolygon.path
                 polygonPath[polygonDrawerPolygon.path.length - 1] = dragCoordinate
+                if (polygonDrawerPolygon.path.length>2){
                     polygonDrawerPolygon.path = polygonPath
                 }
             }
         }
+    }
 
     /// Polygon being drawn
     MapPolygon {