[libxml2] Add a missing argument check

[Daniel Veillard <veillard src gnome org>]

commit 7d2e8c950f1f017f5f3a45f999e5a3aad3e699da
Author: Gaurav Gupta <g gupta samsung com>
Date:   Mon Jul 14 16:08:28 2014 +0800

    Add a missing argument check
    
    For https://bugzilla.gnome.org/show_bug.cgi?id=733042
    
    the states argument of xmlRelaxNGAddStates() ought to be checked too

 relaxng.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/relaxng.c b/relaxng.c
index 1ba4fba..4273db3 100644
--- a/relaxng.c
+++ b/relaxng.c
@@ -1095,7 +1095,7 @@ xmlRelaxNGAddStates(xmlRelaxNGValidCtxtPtr ctxt,
 {
     int i;
 
-    if (state == NULL) {
+    if (state == NULL || states == NULL) {
         return (-1);
     }
     if (states->nbState >= states->maxState) {