Increase the reliability of QueryCredentialsAttribute_Name usage by wrapping a try-finally around the allocation that happens inside the CER.

NSspi/Credentials/Credential.cs

@@ -155,12 +155,18 @@ namespace NSspi.Credentials
                         this.safeCredHandle.DangerousRelease();
 
                         if( status == SecurityStatus.OK && carrier.Name != IntPtr.Zero )
+                        {
+                            try
                             {
                                 name = Marshal.PtrToStringUni( carrier.Name );
+                            }
+                            finally
+                            {
                                 NativeMethods.FreeContextBuffer( carrier.Name );
                             }
                         }
                     }
+                }
 
                 if( status.IsError() )
                 {