Fix polyline update and removal bookkeeping

Fixes CesiumGS#4983.

PolylineCollection stores a list of polylines that are waiting to be updated in the next render pass.  However, if a polyline is both updated _and_ removed in the same synchronous execution sequence, _and_ the polyline is near the end of the collection's internal `this._polylines` list, it's possible for the PolylineCollection to effectively read off the end of the array, causing an error "Batch Table instanceIndex out of range".

This is resolved by ensuring that removing a polyline from the collection also removes it from the list of polylines waiting to be updated.

Source/Scene/PolylineCollection.js

@@ -299,6 +299,12 @@ define([
     PolylineCollection.prototype.remove = function(polyline) {
         if (this.contains(polyline)) {
             this._polylines[polyline._index] = undefined; // Removed later
+
+            var polylineUpdateIndex = this._polylinesToUpdate.indexOf(polyline);
+            if(this._polylinesToUpdate.length && polylineUpdateIndex >= 0) {
+                this._polylinesToUpdate.splice(polylineUpdateIndex, 1);
+            }
+
             this._polylinesRemoved = true;
             this._createVertexArray = true;
             this._createBatchTable = true;