[syslinux:elflink] core/lwip: Fix NULL pointer check

[syslinux-bot for Gene Cumm]

Commit-ID:  ac223941475118b1e819fe260c348559e6e81994
Gitweb:     http://www.syslinux.org/commit/ac223941475118b1e819fe260c348559e6e81994
Author:     Gene Cumm <gene.cumm at gmail.com>
AuthorDate: Wed, 21 Aug 2013 22:21:27 -0400
Committer:  Gene Cumm <gene.cumm at gmail.com>
CommitDate: Mon, 23 Sep 2013 17:25:32 -0400

core/lwip: Fix NULL pointer check

Signed-off-by: Gene Cumm <gene.cumm at gmail.com>

---
 core/lwip/src/arch/sys_arch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/lwip/src/arch/sys_arch.c b/core/lwip/src/arch/sys_arch.c
index 2597bd4..4081d01 100644
--- a/core/lwip/src/arch/sys_arch.c
+++ b/core/lwip/src/arch/sys_arch.c
@@ -48,7 +48,7 @@ u32_t sys_arch_sem_wait(sys_sem_t *sem, u32_t timeout)
 {
     mstime_t rv;
 
-    if (!!sem)
+    if (!sem || !*sem)
 	return SYS_ARCH_TIMEOUT;
     rv = sem_down(*sem, timeout);
     if (rv == (mstime_t)-1)