[libxml2] Add missing Null check in xmlParseExternalEntityPrivate

[Daniel Veillard <veillard src gnome org>]

commit cf77e60515045bdd66f2c59c69a06e603b470eae
Author: Gaurav Gupta <g gupta samsung com>
Date:   Wed Sep 30 14:46:29 2015 +0200

    Add missing Null check in xmlParseExternalEntityPrivate
    
    For https://bugzilla.gnome.org/show_bug.cgi?id=755857
    
    a case where we check for NULL but not everywhere

 parser.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/parser.c b/parser.c
index f1724a9..a65e4cc 100644
--- a/parser.c
+++ b/parser.c
@@ -13367,7 +13367,7 @@ xmlParseExternalEntityPrivate(xmlDocPtr doc, xmlParserCtxtPtr oldctxt,
     /*
      * Also record the size of the entity parsed
      */
-    if (ctxt->input != NULL) {
+    if (ctxt->input != NULL && oldctxt != NULL) {
        oldctxt->sizeentities += ctxt->input->consumed;
        oldctxt->sizeentities += (ctxt->input->cur - ctxt->input->base);
     }
@@ -13379,9 +13379,11 @@ xmlParseExternalEntityPrivate(xmlDocPtr doc, xmlParserCtxtPtr oldctxt,
 
     if (sax != NULL)
        ctxt->sax = oldsax;
-    oldctxt->node_seq.maximum = ctxt->node_seq.maximum;
-    oldctxt->node_seq.length = ctxt->node_seq.length;
-    oldctxt->node_seq.buffer = ctxt->node_seq.buffer;
+    if (oldctxt != NULL) {
+        oldctxt->node_seq.maximum = ctxt->node_seq.maximum;
+        oldctxt->node_seq.length = ctxt->node_seq.length;
+        oldctxt->node_seq.buffer = ctxt->node_seq.buffer;
+    }
     ctxt->node_seq.maximum = 0;
     ctxt->node_seq.length = 0;
     ctxt->node_seq.buffer = NULL;