[libxml2] Fix potential null deref in xmlSchemaIDCFillNodeTables

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 4e326a3aa93b1709118a814c013a0178028dd9a3
Author: zhouzhongyuan <zhouzhongyuan huawei com>
Date:   Mon Sep 2 14:16:12 2019 +0800

    Fix potential null deref in xmlSchemaIDCFillNodeTables
    
    Merge request !45

 xmlschemas.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/xmlschemas.c b/xmlschemas.c
index f3d2664b..457f7d4a 100644
--- a/xmlschemas.c
+++ b/xmlschemas.c
@@ -23366,6 +23366,8 @@ xmlSchemaIDCFillNodeTables(xmlSchemaValidCtxtPtr vctxt,
        * Get/create the IDC binding on this element for the IDC definition.
        */
        bind = xmlSchemaIDCAcquireBinding(vctxt, matcher);
+       if (bind == NULL)
+          goto internal_error;
 
        if (! WXS_ILIST_IS_EMPTY(bind->dupls)) {
            dupls = (xmlSchemaPSVIIDCNodePtr *) bind->dupls->items;