Don't add polyline to update list twice

CHANGES.md

@@ -10,6 +10,7 @@ Change Log
 
 ##### Fixes :wrench:
 * Fixed an issue where `pickPosition` would return incorrect results when called after `sampleHeight` or `clampToHeight`. [#7113](https://github.com/AnalyticalGraphicsInc/cesium/pull/7113)
+* Fixed crash when updating polyline attributes twice in one frame [#7155](https://github.com/AnalyticalGraphicsInc/cesium/pull/7155)
 * Fixed a crash when using `BingMapsGeocoderService` [#7143](https://github.com/AnalyticalGraphicsInc/cesium/issues/7143)
 
 ### 1.50 - 2018-10-01

Source/Scene/PolylineCollection.js

@@ -1128,7 +1128,9 @@ define([
 
     PolylineCollection.prototype._updatePolyline = function(polyline, propertyChanged) {
         this._polylinesUpdated = true;
-        this._polylinesToUpdate.push(polyline);
+        if (!polyline._dirty) {
+            this._polylinesToUpdate.push(polyline);
+        }
         ++this._propertiesChanged[propertyChanged];
     };
 

Specs/Scene/PolylineCollectionSpec.js

@@ -343,6 +343,21 @@ defineSuite([
         expect(polylines._polylinesToUpdate.length).toEqual(1);
     });
 
+    it('only adds polyline to the update list once', function() {
+        var firstPolyline = polylines.add();
+        var secondPolyline = polylines.add();
+
+        firstPolyline.width = 4;
+        secondPolyline.width = 5;
+        secondPolyline.width = 7;
+
+        expect(polylines._polylinesToUpdate.length).toEqual(2);
+
+        polylines.remove(secondPolyline);
+
+        expect(polylines._polylinesToUpdate.length).toEqual(1);
+    });
+
     it('can check if it contains a polyline', function() {
         var polyline = polylines.add();