[NetworkManager-openconnect] Fix crash on XML parse failure

[David Woodhouse <dwmw2 src gnome org>]

commit ad09947da5e91a57fba461068636a44ea487ab0c
Author: David Woodhouse <dwmw2 infradead org>
Date:   Tue Oct 16 09:55:01 2018 -0700

    Fix crash on XML parse failure

 auth-dialog/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/auth-dialog/main.c b/auth-dialog/main.c
index 65b55e6..d87f39b 100644
--- a/auth-dialog/main.c
+++ b/auth-dialog/main.c
@@ -956,7 +956,8 @@ static int parse_xmlconfig(gchar *xmlconfig)
        }
 
        xml_doc = xmlReadMemory(xmlconfig, strlen(xmlconfig), "noname.xml", NULL, 0);
-
+       if (!xml_doc)
+               return -EIO;
        xml_node = xmlDocGetRootElement(xml_doc);
        for (xml_node = xml_node->children; xml_node; xml_node = xml_node->next) {
                 if (xml_node->type == XML_ELEMENT_NODE &&