core/lwip: Fix NULL pointer check

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

diff --git a/core/lwip/src/arch/sys_arch.c b/core/lwip/src/arch/sys_arch.c
index 2597bd4..4081d01 100644 (file)
--- 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)