Fix snapping when polyline has only one coordinate (#1526) (patch)

cypress/integration/line.spec.js

@@ -358,4 +358,20 @@ describe('Draw & Edit Line', () => {
     cy.hasVertexMarkers(3);
     cy.hasMiddleMarkers(2);
   });
+
+  it('snapping doesn\'t throw an error when Polyline has only one coordinate' , () => {
+    cy.window().then(({ map, L }) => {
+      L.polyline([map.getCenter()]).addTo(map);
+    });
+
+    // activate line drawing
+    cy.toolbarButton('polyline')
+      .click()
+      .closest('.button-container')
+      .should('have.class', 'active');
+
+    // draw a line
+    cy.get(mapSelector)
+      .click(150, 250)
+  });
 });

src/js/Mixins/Snapping.js

@@ -284,6 +284,10 @@ const SnapMixin = {
       if (layer._parentCopy && layer._parentCopy === this._layer) {
         return;
       }
+      // if a polyline has only one coordinate
+      if (layer.getLatLngs?.().flat(5).length < 2) {
+        return;
+      }
       // find the closest latlng, segment and the distance of this layer to the dragged marker latlng
       const results = this._calcLayerDistances(latlng, layer);
       results.distance = Math.floor(results.distance);