fix a bug in cs_close(): improper check on handle value
diff --git a/cs.c b/cs.c
index a96b435..e7e13b9 100644
--- a/cs.c
+++ b/cs.c
@@ -179,7 +179,7 @@
 
 cs_err cs_close(csh *handle)
 {
-	if (*handle)
+	if (*handle == 0)
 		// invalid handle
 		return CS_ERR_CSH;