Avoid some theoretical null pointer derefs

FPEngine.cc

@@ -1366,7 +1366,9 @@ int FPHost::choose_osscan_ports() {
       if ((tport = this->target_host->ports.nextPort(tport, &port, IPPROTO_TCP, PORT_OPEN)))
        this->open_port_tcp = tport->portno;
     }
+    if (this->target_host->FPR != NULL) {
       this->target_host->FPR->osscan_opentcpport = this->open_port_tcp;
+    }
   } else {
     /* If we don't have an open port, set it to -1 so we don't send probes that
      * target TCP open ports */
@@ -1382,7 +1384,9 @@ int FPHost::choose_osscan_ports() {
     if (tport->portno == 0)
       if ((tport = this->target_host->ports.nextPort(tport, &port, IPPROTO_TCP, PORT_CLOSED)))
         this->closed_port_tcp = tport->portno;
+    if (this->target_host->FPR != NULL) {
       this->target_host->FPR->osscan_closedtcpport = this->closed_port_tcp;
+    }
   } else if ((tport = this->target_host->ports.nextPort(NULL, &port, IPPROTO_TCP, PORT_UNFILTERED))) {
     /* Well, we will settle for unfiltered */
     this->closed_port_tcp = tport->portno;
@@ -1405,7 +1409,9 @@ int FPHost::choose_osscan_ports() {
     if (tport->portno == 0)
       if ((tport = this->target_host->ports.nextPort(tport, &port, IPPROTO_UDP, PORT_CLOSED)))
         this->closed_port_udp = tport->portno;
+    if (this->target_host->FPR != NULL) {
       this->target_host->FPR->osscan_closedudpport = this->closed_port_udp;
+    }
   } else if ((tport = this->target_host->ports.nextPort(NULL, &port, IPPROTO_UDP, PORT_UNFILTERED))) {
     /* Well, we will settle for unfiltered */
     this->closed_port_udp = tport->portno;

nmap_dns.cc

@@ -499,6 +499,7 @@ static void do_possible_writes() {
         servI->to_process.pop_front();
       } else if (!new_reqs.empty()) {
         tpreq = new_reqs.front();
+        assert(tpreq != NULL);
         tpreq->first_server = tpreq->curr_server = &*servI;
         new_reqs.pop_front();
       }

nsock/src/nsock_core.c

@@ -322,6 +322,7 @@ void handle_connect_result(struct npool *ms, struct nevent *nse, enum nse_status
   int optval;
   socklen_t optlen = sizeof(int);
   struct niod *iod = nse->iod;
+  assert(iod != NULL);
 #if HAVE_OPENSSL
   int sslerr;
   int rc = 0;

nsock/src/nsock_proxy.c

@@ -139,6 +139,7 @@ void nsock_proxychain_delete(nsock_proxychain chain) {
 
 int nsock_pool_set_proxychain(nsock_pool nspool, nsock_proxychain chain) {
   struct npool *nsp = (struct npool *)nspool;
+  assert(nsp != NULL);
 
   if (nsp && nsp->px_chain) {
     nsock_log_error("Invalid call. Existing proxychain on this nsock_pool");