[Az.Resources] Do not error out when AppId is null (#25110)

* Update ActiveDirectoryClientExtensions.cs

* Update PSADServicePrincipal.cs

* Update src/Resources/Resources/ActiveDirectory/Models/ActiveDirectoryClientExtensions.cs

Co-authored-by: Yabo Hu <[email protected]>

---------

Co-authored-by: Yabo Hu <[email protected]>

Author: NoriZC

src/Resources/Resources/ActiveDirectory/Models/ActiveDirectoryClientExtensions.cs

@@ -103,7 +103,7 @@ public static PSADServicePrincipal ToPSADServicePrincipal(this MicrosoftGraphSer
                 DisplayName = servicePrincipal.DisplayName,
                 Id = servicePrincipal.Id,
                 DeletionTimestamp = servicePrincipal.DeletedDateTime,
-                ApplicationId = Guid.Parse(servicePrincipal.AppId),
+                ApplicationId = String.IsNullOrEmpty(servicePrincipal.AppId)? (Guid?)null : Guid.Parse(servicePrincipal.AppId),
                 Type = "ServicePrincipal",
                 ServicePrincipalNames = servicePrincipal.ServicePrincipalNames.ToArray(),
                 AdditionalProperties = servicePrincipal.AdditionalProperties

src/Resources/Resources/ActiveDirectory/Models/PSADServicePrincipal.cs

@@ -20,7 +20,7 @@ public class PSADServicePrincipal : PSADObject
     {
         public string[] ServicePrincipalNames { get; set; }
 
-        public Guid ApplicationId { get; set; }
+        public Guid? ApplicationId { get; set; }
 
         public string ObjectType => "ServicePrincipal";
     }