syslogd: fix shmat error check

diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index f8e8488..345bf0e 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -218,7 +218,7 @@
 	}
 
 	G.shbuf = shmat(G.shmid, NULL, 0);
-	if (!G.shbuf) {
+	if (G.shbuf == (void*) -1L) { /* shmat has bizarre error return */
 		bb_perror_msg_and_die("shmat");
 	}