[evolution-data-server] Avoid a crash in camel_session_get_service_by_url().

[Matthew Barnes <mbarnes src gnome org>]

commit 13c8e07865d1e6f04b7c477c8713c69efdbb519c
Author: Matthew Barnes <mbarnes redhat com>
Date:   Fri Oct 21 21:45:02 2011 -0400

    Avoid a crash in camel_session_get_service_by_url().
    
    Check that we found a CamelProvider before dereferencing it.

 camel/camel-session.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/camel/camel-session.c b/camel/camel-session.c
index f074852..983ae39 100644
--- a/camel/camel-session.c
+++ b/camel/camel-session.c
@@ -916,6 +916,9 @@ camel_session_get_service_by_url (CamelSession *session,
 		provider = camel_service_get_provider (service);
 		service_url = camel_service_get_camel_url (service);
 
+		if (provider == NULL)
+			continue;
+
 		if (provider->url_equal == NULL)
 			continue;