Fix a null reference exception with extensible template deployment (Azure#19783)

* Add symbolic name test

* Add extensibility test, fix null ref bug

* Add changelog entry

* Update ChangeLog.md

Co-authored-by: Yabo Hu <yabhu@microsoft.com>

Author: anthony-c-martin

src/Resources/ResourceManager/SdkClient/ResourceManagerSdkClient.cs

@@ -355,7 +355,7 @@ private List<DeploymentOperation> GetNewOperations(List<DeploymentOperation> old
                 }
 
                 //If nested deployment, get the operations under those deployments as well
-                if (operation.Properties.TargetResource != null && operation.Properties.TargetResource.ResourceType.Equals(Constants.MicrosoftResourcesDeploymentType, StringComparison.OrdinalIgnoreCase))
+                if (operation.Properties.TargetResource?.ResourceType?.Equals(Constants.MicrosoftResourcesDeploymentType, StringComparison.OrdinalIgnoreCase) == true)
                 {
                     HttpStatusCode statusCode;
                     Enum.TryParse<HttpStatusCode>(operation.Properties.StatusCode, out statusCode);

src/Resources/Resources.Test/ScenarioTests/DeploymentTests.cs

@@ -230,5 +230,19 @@ public void TestNewDeploymentFromTemplateAndParameterFileContainingTagsOutput()
         {
             TestRunner.RunTestScript("Test-NewDeploymentFromTemplateAndParameterFileContainingTagsOutput");
         }
+
+        [Fact]
+        [Trait(Category.AcceptanceType, Category.CheckIn)]
+        public void TestSymbolicNameDeployment()
+        {
+            TestRunner.RunTestScript("Test-SymbolicNameDeployment");
+        }
+
+        [Fact]
+        [Trait(Category.AcceptanceType, Category.CheckIn)]
+        public void TestExtensibleResourceDeployment()
+        {
+            TestRunner.RunTestScript("Test-ExtensibleResourceDeployment");
+        }
     }
 }