fixed xmlSaveFormatFileEnc() when encoding == NULL Fixes bug #67229 Daniel

* tree.c: fixed xmlSaveFormatFileEnc() when encoding == NULL
  Fixes bug #67229
Daniel
diff --git a/tree.c b/tree.c
index ab8532b..e2d599a 100644
--- a/tree.c
+++ b/tree.c
@@ -6603,6 +6603,9 @@
     xmlCharEncoding enc;
     int ret;
 
+    if (encoding == NULL)
+	encoding = (const char *) cur->encoding;
+
     if (encoding != NULL) {
 
 	enc = xmlParseCharEncoding(encoding);