diff --git a/src/util/qpolygon-utils.js b/src/util/qpolygon-utils.js
index cded90ee..34bc2320 100644
--- a/src/util/qpolygon-utils.js
+++ b/src/util/qpolygon-utils.js
@@ -305,6 +305,9 @@ export function removeDuplicatePolygons(polygons) {
 }
 
 export const isSamePoint = (a, b) => {
+  if (!a || !b) {
+    return false
+  }
   return Math.abs(Math.round(a.x) - Math.round(b.x)) <= 2 && Math.abs(Math.round(a.y) - Math.round(b.y)) <= 2
 }