silence coverity

src/lib/ares_event_poll.c

@@ -77,6 +77,9 @@ static size_t ares_evsys_poll_wait(ares_event_thread_t *e,
 
   if (fdlist != NULL && num_fds) {
     pollfd = ares_malloc_zero(sizeof(*pollfd) * num_fds);
+    if (pollfd == NULL) {
+      goto done;
+    }
     for (i = 0; i < num_fds; i++) {
       const ares_event_t *ev =
         ares__htable_asvp_get_direct(e->ev_handles, fdlist[i]);