[libxml2] xmlschemastypes.c: xmlSchemaGetFacetValueAsULong add, check "facet->val"

[Nick Wellnhofer <nwellnhof src gnome org>]

commit cb7a572b3e7f568f1ebc8d91b1b8826a8ce3baa8
Author: Xiaoming Ni <nixiaoming huawei com>
Date:   Mon Dec 7 20:17:34 2020 +0800

    xmlschemastypes.c: xmlSchemaGetFacetValueAsULong add, check "facet->val"
    
    The xmlSchemaGetFacetValueAsUlong() API is an external API.
    The validity of external input parameters must be strictly verified.
    Before accessing "facet->val->value", we need check whether "facet->val" is
    a null pointer.
    
    Signed-off-by: wuqing <wuqing30 huawei com>
    Signed-off-by: Xiaoming Ni <nixiaoming huawei com>

 xmlschemastypes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/xmlschemastypes.c b/xmlschemastypes.c
index d6b9f924..07b5fd76 100644
--- a/xmlschemastypes.c
+++ b/xmlschemastypes.c
@@ -5142,7 +5142,7 @@ xmlSchemaGetFacetValueAsULong(xmlSchemaFacetPtr facet)
     /*
     * TODO: Check if this is a decimal.
     */
-    if (facet == NULL)
+    if (facet == NULL || facet->val == NULL)
         return 0;
     return ((unsigned long) facet->val->value.decimal.lo);
 }