From f48704cac4b42f7ace9c71f15d1c7fefb24c3ddd Mon Sep 17 00:00:00 2001
From: mike-000 <49240900+mike-000@users.noreply.github.com>
Date: Wed, 1 Jan 2020 21:04:12 +0000
Subject: [PATCH] Fix for undefined source in Vector layer

A source left or set undefined is equivalent to an empty source so treat it as such to prevent errors in prepareFrame
---
 src/ol/renderer/canvas/VectorLayer.js | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/ol/renderer/canvas/VectorLayer.js b/src/ol/renderer/canvas/VectorLayer.js
index b451a01b88..3915ba8a66 100644
--- a/src/ol/renderer/canvas/VectorLayer.js
+++ b/src/ol/renderer/canvas/VectorLayer.js
@@ -11,6 +11,16 @@ import CanvasLayerRenderer from './Layer.js';
 import {defaultOrder as defaultRenderOrder, getTolerance as getRenderTolerance, getSquaredTolerance as getSquaredRenderTolerance, renderFeature} from '../vector.js';
 import {toString as transformToString, makeScale, makeInverse, apply} from '../../transform.js';
 import {createHitDetectionImageData, hitDetect} from '../../render/canvas/hitdetect.js';
+import VectorSource from '../../source/Vector.js';
+
+
+/**
+ * @const
+ * @type {VectorSource}
+ * @private
+ */
+const emptySource = new VectorSource();
+
 
 /**
  * @classdesc
@@ -328,7 +338,7 @@ class CanvasVectorLayerRenderer extends CanvasLayerRenderer {
    */
   prepareFrame(frameState) {
     const vectorLayer = this.getLayer();
-    const vectorSource = vectorLayer.getSource();
+    const vectorSource = vectorLayer.getSource() || emptySource;
 
     const animating = frameState.viewHints[ViewHint.ANIMATING];
     const interacting = frameState.viewHints[ViewHint.INTERACTING];