Fix more potential null-ptr-derefs in use of gethostbyname()

No known sightings of these sites actually being the location of a segfault,
but as we learned from the segfaults in rblchk(), the first entry in the
h_addr_list can be NULL in some cases.

src/sbbs3/ftpsrvr.c

@@ -3024,7 +3024,8 @@ static void ctrl_thread(void* arg)
 				ip_addr=0;
 				/* TODO: IPv6 this here lookup */
 				if(startup->options&FTP_OPT_LOOKUP_PASV_IP
-					&& (host=gethostbyname(server_host_name()))!=NULL)
+					&& (host=gethostbyname(server_host_name()))!=NULL
+					&& host->h_addr_list[0] != NULL)
 					ip_addr=ntohl(*((ulong*)host->h_addr_list[0]));
 				if(ip_addr==0 && (ip_addr=startup->pasv_ip_addr.s_addr)==0)
 					ip_addr=ntohl(pasv_addr.in.sin_addr.s_addr);

src/sbbs3/mailsrvr.c

@@ -943,6 +943,9 @@ static u_long resolve_ip(const char *inaddr)
 	if((host=gethostbyname(inaddr))==NULL)
 		return((u_long)INADDR_NONE);
 
+	if(host->h_addr_list[0] == NULL)
+		return (u_long)INADDR_NONE;
+
 	return(*((ulong*)host->h_addr_list[0]));
 }
 

src/sbbs3/main.cpp

@@ -381,6 +381,8 @@ u_long resolve_ip(char *addr)
 		return(inet_addr(addr));
 	if((host=gethostbyname(addr))==NULL)
 		return((u_long)INADDR_NONE);
+	if(host->h_addr_list[0] == NULL)
+		return (u_long)INADDR_NONE;
 	return(*((ulong*)host->h_addr_list[0]));
 }