Add support empty NoteProperty in Group-Object (#9109)

src/Microsoft.PowerShell.Commands.Utility/commands/utility/ObjectCommandComparer.cs

@@ -113,12 +113,17 @@ namespace Microsoft.PowerShell.Commands
         public override int GetHashCode()
         {
             if (PropertyValue == null)
+            {
                 return 0;
+            }
 
             object baseObject = PSObject.Base(PropertyValue);
-            IComparable baseObjectComparable = baseObject as IComparable;
+            if (baseObject == null)
+            {
+                return 0;
+            }
 
-            if (baseObjectComparable != null)
+            if (baseObject is IComparable)
             {
                 return baseObject.GetHashCode();
             }

test/powershell/Modules/Microsoft.PowerShell.Utility/Group-Object.Tests.ps1

@@ -123,6 +123,13 @@ Describe "Group-Object" -Tags "CI" {
         $result['Successful'].ErrorMessage.Count | Should -Be 4
         $result['Successful'].ErrorMessage[0] | Should -Be ''
     }
+
+    It "Should understand empty NoteProperty" {
+        $result = "dummy" | Select-Object -Property @{Name = 'X'; Expression = {}} | Group-Object X
+        $result.Count | Should -Be 1
+        $result[0].Name | Should -Be ""
+        $result[0].Group | Should -Be '@{X=}'
+    }
 }
 
 Describe "Check 'Culture' parameter in order object cmdlets (Group-Object, Sort-Object, Compare-Object)" -Tags "CI" {