Added update to legend test.

samples/unit-tests/legend/layout/demo.js

@@ -1,6 +1,7 @@
 QUnit.test('Legend layout', function (assert) {
     var chart = Highcharts.chart('container', {
         legend: {
+            enabled: false,
             layout: 'proximate',
             align: 'right'
         },
@@ -34,6 +35,13 @@ QUnit.test('Legend layout', function (assert) {
         ]
     });
 
+    // We should be able to update the legend.enabled property, #19078.
+    chart.update({
+        legend: {
+            enabled: true
+        }
+    });
+
     chart.series.forEach(function (s) {
         var y = s.points[2].plotY || s.yAxis.height;
 
@@ -102,6 +110,7 @@ QUnit.test('Proximate layout and dataGrouping', assert => {
             animation: false
         },
         legend: {
+            enabled: true,
             align: 'right',
             layout: 'proximate'
         },
@@ -135,6 +144,19 @@ QUnit.test('Proximate layout and dataGrouping', assert => {
         ]
     });
 
+    // These updates should not cause an error, #19028.
+    chart.update({
+        legend: {
+            enabled: false
+        }
+    });
+
+    chart.update({
+        legend: {
+            enabled: true
+        }
+    });
+
     chart.series[1].hide();
 
     // Avoid using strict position as it may vary between browsers