Always attempt to correctly release the session.

Author: Hubert Plociniczak

src/client/impl/ModelBase.cs

@@ -469,8 +469,11 @@ public void HandleChannelClose(ushort replyCode,
                              methodId));
 
             m_session.Close(m_closeReason, false);
-            _Private_ChannelCloseOk();
-            m_session.Notify();
+            try {
+                _Private_ChannelCloseOk();
+            } finally {
+                m_session.Notify();
+            }
         }
 
         public void FinishClose()