Fill the undefined parts of AveragesMap chart.

src/components/header/AveragesMap.vue

@@ -291,6 +291,11 @@ export default {
           return // the stick 'stickID' is outside view of the camera 'cameraID'
         }
         const snowHeightAverage = image.sticks[stickID].snowHeightAverage
+
+        // Draw a straight line between identified points, ignoring the undefined ones.
+        if (snowHeightAverage === -1) {
+          continue
+        }
         if (lastTimestamp != null) {
           this.drawLine(
             context,