fix SSU2 crash on shutdown

libi2pd/SSU2.cpp

@@ -88,27 +88,34 @@ namespace transport
 
 	void SSU2Server::Stop ()
 	{
-		for (auto& it: m_Sessions)
+		if (IsRunning ())
+		{	
+			m_TerminationTimer.cancel ();
+			m_ResendTimer.cancel ();
+			m_IntroducersUpdateTimer.cancel ();
+			m_IntroducersUpdateTimerV6.cancel ();
+		}	
+		
+		auto sessions = m_Sessions;
+		for (auto& it: sessions)
 		{	
 			it.second->RequestTermination (eSSU2TerminationReasonRouterShutdown);
 			it.second->Done ();
 		}	
-		m_Sessions.clear ();
-		m_SessionsByRouterHash.clear ();
-		m_PendingOutgoingSessions.clear ();
-		m_Relays.clear ();
-		m_Introducers.clear ();
-		m_IntroducersV6.clear ();
 		
 		if (context.SupportsV4 () || context.SupportsV6 ())
 			m_ReceiveService.Stop ();
-
 		m_SocketV4.close ();
 		m_SocketV6.close ();
-		if (IsRunning ())
-			m_TerminationTimer.cancel ();
 		
 		StopIOService ();
+
+		m_Sessions.clear ();
+		m_SessionsByRouterHash.clear ();
+		m_PendingOutgoingSessions.clear ();
+		m_Relays.clear ();
+		m_Introducers.clear ();
+		m_IntroducersV6.clear ();
 	}
 
 	void SSU2Server::SetLocalAddress (const boost::asio::ip::address& localAddress)