[glib] gtlscertificate: Fix error reporting if a GError is not passed in

[Philip Withnall <pwithnall src gnome org>]

commit 292fd1155ae502df9aadc343cdbbd5d6b3149090
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Sat Oct 3 10:58:18 2015 +0100

    gtlscertificate: Fix error reporting if a GError is not passed in
    
    If the certificate constructor is called as:
       g_tls_certificate_new_from_pem (data, length, NULL);
    and PEM parsing fails for the private key, the function would have
    continued to try and create a certificate using a NULL key_pem value,
    which would have failed or crashed.
    
    Use g_propagate_error() correctly to avoid this.
    
    Coverity CID: 1325403

 gio/gtlscertificate.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/gio/gtlscertificate.c b/gio/gtlscertificate.c
index d7dff70..e43c2ce 100644
--- a/gio/gtlscertificate.c
+++ b/gio/gtlscertificate.c
@@ -471,17 +471,22 @@ g_tls_certificate_new_from_pem  (const gchar  *data,
                                 gssize        length,
                                 GError      **error)
 {
+  GError *child_error = NULL;
   gchar *key_pem;
   GTlsCertificate *cert;
 
   g_return_val_if_fail (data != NULL, NULL);
+  g_return_val_if_fail (error == NULL || *error == NULL, NULL);
 
   if (length == -1)
     length = strlen (data);
 
-  key_pem = parse_private_key (data, length, FALSE, error);
-  if (error && *error)
-    return NULL;
+  key_pem = parse_private_key (data, length, FALSE, &child_error);
+  if (child_error != NULL)
+    {
+      g_propagate_error (error, child_error);
+      return NULL;
+    }
 
   cert = parse_and_create_certificate (data, length, key_pem, error);
   g_free (key_pem);