Removed null reference to Graph Instance environment after calling Invoke-MgGraph command (#1328)

* Reassigned _originalEnvironment variable to the previous user defined state instead of pointing to null

* Corrected comment on Remove-MgEnvironment command

Co-authored-by: Timothy Wamalwa <twamalwa@microsoft.com>
Co-authored-by: Peter Ombwa <peombwa@microsoft.com>

Author: 3 people

src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs

@@ -1090,9 +1090,13 @@ private string QualifyFilePath(string path)
 
         /// <summary>
         ///     Resets GraphSession environment back to its original state.
+        ///     Original state can remain to be the previous state defined by the user, 
+        ///     or the default global state. User defined state can be removed by calling,
+        ///     Remove-MgEnvironment Command
         /// </summary>
         private void ResetGraphSessionEnvironment()
         {
+            _originalEnvironment = GraphSession.Instance.Environment;
             GraphSession.Instance.Environment = _originalEnvironment;
         }