Stopped crash on destruction of GeoJSONLayer

dist/vizicities.js

@@ -14255,6 +14255,18 @@ return /******/ (function(modules) { // webpackBootstrap
 	        this._pickingMesh = null;
 	      }
 	
+	      if (this._polygonMesh) {
+	        this._polygonMesh = null;
+	      }
+	
+	      if (this._polylineMesh) {
+	        this._polylineMesh = null;
+	      }
+	
+	      if (this._pointMesh) {
+	        this._pointMesh = null;
+	      }
+	
 	      // Run common destruction logic from parent
 	      _get(Object.getPrototypeOf(GeoJSONLayer.prototype), 'destroy', this).call(this);
 	    }
@@ -14340,11 +14352,14 @@ return /******/ (function(modules) { // webpackBootstrap
 	  }, {
 	    key: 'destroy',
 	    value: function destroy() {
-	      for (var i = 0; i < this._layers.length; i++) {
-	        this._layers[i].destroy();
-	      }
+	      // TODO: Sometimes this is already null, find out why
+	      if (this._layers) {
+	        for (var i = 0; i < this._layers.length; i++) {
+	          this._layers[i].destroy();
+	        }
 	
-	      this._layers = null;
+	        this._layers = null;
+	      }
 	
 	      _get(Object.getPrototypeOf(LayerGroup.prototype), 'destroy', this).call(this);
 	    }

src/layer/GeoJSONLayer.js

@@ -493,6 +493,18 @@ class GeoJSONLayer extends LayerGroup {
       this._pickingMesh = null;
     }
 
+    if (this._polygonMesh) {
+      this._polygonMesh = null;
+    }
+
+    if (this._polylineMesh) {
+      this._polylineMesh = null;
+    }
+
+    if (this._pointMesh) {
+      this._pointMesh = null;
+    }
+
     // Run common destruction logic from parent
     super.destroy();
   }

src/layer/LayerGroup.js

@@ -34,11 +34,14 @@ class LayerGroup extends Layer {
 
   // Destroy the layers and remove them from the scene and memory
   destroy() {
-    for (var i = 0; i < this._layers.length; i++) {
-      this._layers[i].destroy();
-    }
+    // TODO: Sometimes this is already null, find out why
+    if (this._layers) {
+      for (var i = 0; i < this._layers.length; i++) {
+        this._layers[i].destroy();
+      }
 
-    this._layers = null;
+      this._layers = null;
+    }
 
     super.destroy();
   }