[gnome-online-accounts] provider: Add warning when backend is broken

[Debarshi Ray <debarshir src gnome org>]

commit 0079611de9355fc7f3000a1bdc132737fad5f347
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Jul 4 14:11:36 2017 +0200

    provider: Add warning when backend is broken
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784512

 src/goabackend/goaprovider.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/src/goabackend/goaprovider.c b/src/goabackend/goaprovider.c
index 35ba0f1..1c0834d 100644
--- a/src/goabackend/goaprovider.c
+++ b/src/goabackend/goaprovider.c
@@ -872,6 +872,14 @@ goa_provider_ensure_credentials_sync (GoaProvider     *self,
   ret = GOA_PROVIDER_GET_CLASS (self)->ensure_credentials_sync (self, object, out_expires_in, cancellable, 
error);
 
  out:
+  if (!ret && error != NULL && *error == NULL)
+    {
+      const gchar *provider_type;
+
+      provider_type = goa_provider_get_provider_type (self);
+      g_critical ("GoaProvider (%s) failed to set error correctly", provider_type);
+    }
+
   g_clear_object (&account);
   return ret;
 }