fixed crash

SSU.cpp

@@ -256,6 +256,7 @@ namespace transport
 
 	std::shared_ptr<SSUSession> SSUServer::FindSession (const boost::asio::ip::udp::endpoint& e) const
 	{
+		std::unique_lock<std::mutex> l(m_SessionsMutex);
 		auto it = m_Sessions.find (e);
 		if (it != m_Sessions.end ())
 			return it->second;

SSU.h

@@ -96,7 +96,7 @@ namespace transport
 			boost::asio::ip::udp::socket m_Socket, m_SocketV6;
 			boost::asio::deadline_timer m_IntroducersUpdateTimer, m_PeerTestsCleanupTimer;
 			std::list<boost::asio::ip::udp::endpoint> m_Introducers; // introducers we are connected to
-			std::mutex m_SessionsMutex;
+			mutable std::mutex m_SessionsMutex;
 			std::map<boost::asio::ip::udp::endpoint, std::shared_ptr<SSUSession> > m_Sessions;
 			std::map<uint32_t, boost::asio::ip::udp::endpoint> m_Relays; // we are introducer
 			std::map<uint32_t, PeerTest> m_PeerTests; // nonce -> creation time in milliseconds

SSUSession.cpp

@@ -1076,7 +1076,14 @@ namespace transport
 			uint8_t buf[48 + 18];
 			// encrypt message with session key
 			FillHeaderAndEncrypt (PAYLOAD_TYPE_SESSION_DESTROYED, buf, 48);
-			Send (buf, 48);
+			try
+			{
+				Send (buf, 48);
+			}
+			catch (std::exception& ex)
+			{
+				LogPrint (eLogError, "SSU send session destoriyed exception ", ex.what ()); 
+			}
 			LogPrint (eLogDebug, "SSU session destroyed sent");
 		}
 	}