Support JS invocations that return undefined

samples/MonoSanityClient/Examples.cs

@@ -37,7 +37,7 @@ namespace MonoSanityClient
                 return $".NET got exception: {result}";
             }
 
-            return $".NET received: {result}";
+            return $".NET received: {(result ?? "(NULL)")}";
         }
     }
 }

src/Microsoft.Blazor.Browser/Renderer.cs

@@ -7,7 +7,7 @@ namespace Microsoft.Blazor.Browser
     {
         public Renderer()
         {
-            WebAssembly.Runtime.EvaluateJavaScript("console.log('Renderer'), 'done'");
+            WebAssembly.Runtime.EvaluateJavaScript("console.log('Renderer')");
         }
     }
 }

test/Microsoft.Blazor.E2ETest/Tests/MonoSanityTest.cs

@@ -81,6 +81,26 @@ namespace Microsoft.Blazor.E2ETest.Tests
             Assert.Contains("at triggerJsException", result);
         }
 
+        [Fact]
+        public void CanEvaluateJsExpressionThatResultsInNull()
+        {
+            Navigate("/", noReload: true);
+            SetValue(Browser, "callJsEvalExpression", "null");
+            Browser.FindElement(By.CssSelector("#callJs button")).Click();
+            var result = GetValue(Browser, "callJsResult");
+            Assert.Equal(".NET received: (NULL)", result);
+        }
+
+        [Fact]
+        public void CanEvaluateJsExpressionThatResultsInUndefined()
+        {
+            Navigate("/", noReload: true);
+            SetValue(Browser, "callJsEvalExpression", "console.log('Not returning anything')");
+            Browser.FindElement(By.CssSelector("#callJs button")).Click();
+            var result = GetValue(Browser, "callJsResult");
+            Assert.Equal(".NET received: (NULL)", result);
+        }
+
         private static string GetValue(IWebDriver webDriver, string elementId)
         {
             var element = webDriver.FindElement(By.Id(elementId));