[libxml2] Fix error message when processing XIncludes with fallbacks

[Nick Wellnhofer <nwellnhof src gnome org>]

commit e32afd3fd7785d861066dd06f93266cb6f433969
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Fri Sep 13 15:45:21 2019 +0200

    Fix error message when processing XIncludes with fallbacks
    
    Fixes bug #616491
    https://bugzilla.gnome.org/show_bug.cgi?id=616491
    
    Based on merge request !41

 xinclude.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/xinclude.c b/xinclude.c
index 53aa3e95..b8e84ec3 100644
--- a/xinclude.c
+++ b/xinclude.c
@@ -1964,6 +1964,7 @@ static int
 xmlXIncludeLoadFallback(xmlXIncludeCtxtPtr ctxt, xmlNodePtr fallback, int nr) {
     xmlXIncludeCtxtPtr newctxt;
     int ret = 0;
+    int oldNbErrors = ctxt->nbErrors;
 
     if ((fallback == NULL) || (fallback->type == XML_NAMESPACE_DECL) ||
         (ctxt == NULL))
@@ -1980,7 +1981,7 @@ xmlXIncludeLoadFallback(xmlXIncludeCtxtPtr ctxt, xmlNodePtr fallback, int nr) {
        newctxt->base = xmlStrdup(ctxt->base);  /* Inherit the base from the existing context */
        xmlXIncludeSetFlags(newctxt, ctxt->parseFlags);
        ret = xmlXIncludeDoProcess(newctxt, ctxt->doc, fallback->children);
-       if (ctxt->nbErrors > 0)
+       if (ctxt->nbErrors > oldNbErrors)
            ret = -1;
        else if (ret > 0)
            ret = 0;    /* xmlXIncludeDoProcess can return +ve number */