attempt to fix a plethora of buffer overflows when trying to connect to a server that does not exist

ex: if you typo´d the serveraddress
this really aint pretty but idk how to make things not turn into limbo hell otherwise

src/d_clisrv.c

@@ -2845,6 +2845,20 @@ static void Command_connect(void)
 		}
 		else
 			CONS_Alert(CONS_ERROR, M_GetText("There is no network driver\n"));
+
+		// invalid address
+		if (servernode == -1)
+		{
+			D_QuitNetGame(); // this will also call D_CloseConnection for us
+			CL_Reset();
+			servernode = 0; // not sure if this is cool, but if this is -1 then bad things happen in alot of networking code
+			multiplayer = false;
+			netgame = false;
+
+			D_StartTitle();
+			M_StartMessage(M_GetText("Failed to connect to server\nMake sure you put in a valid Address!\n"), NULL, MM_NOTHING);
+			return;
+		}
 	}
 
 	CV_Set(&cv_lastserver, I_GetNodeAddress(servernode));

src/i_tcp.c

@@ -452,13 +452,21 @@ static const char *SOCK_GetNodeAddress(INT32 node)
 {
 	if (node == 0)
 		return "self";
+
+	if (node < 0 || node > MAXNETNODES)
+		return NULL;
+
 	if (!nodeconnected[node])
 		return NULL;
+
 	return SOCK_AddrToStr(&clientaddress[node]);
 }
 
 static UINT32 SOCK_GetNodeAddressInt(INT32 node)
 {
+	if (node < 0 || node > MAXNETNODES)
+		return 0;
+
 	if (nodeconnected[node] && clientaddress[node].any.sa_family == AF_INET)
 	{
 		return clientaddress[node].ip4.sin_addr.s_addr;