Check for presence of thr in icarus get nonce for startup nonce testing to work.
diff --git a/driver-icarus.c b/driver-icarus.c
index 5b0af8d..43a460e 100644
--- a/driver-icarus.c
+++ b/driver-icarus.c
@@ -497,7 +497,7 @@ static int icarus_get_nonce(struct cgpu_info *icarus, unsigned char *buf, struct
return ICA_NONCE_OK;
rc = SECTOMS(tdiff(tv_finish, tv_start));
- if (thr->work_restart) {
+ if (thr && thr->work_restart) {
applog(LOG_DEBUG, "Icarus Read: Work restart at %d ms", rc);
return ICA_NONCE_RESTART;
}