fix warning will POLL_HACK
diff --git a/strace.c b/strace.c
index f88525d..9bd708a 100644
--- a/strace.c
+++ b/strace.c
@@ -1412,7 +1412,7 @@
 trace()
 {
 #ifdef POLL_HACK
-	struct tcb *in_syscall;
+	struct tcb *in_syscall = NULL;
 #endif
 	struct tcb *tcp;
 	int pfd;