Avoid crash in e_book_backend_file_load_revision()

There could happen a crash in e_book_backend_file_load_revision()
due to NULL 'error' when an application did a quick open/close
operations, in which case a backend was reused, with already set
priv::revision, and the call failed on a runtime constraint, but
didn't set the 'error', which led to the crash.

diff --git a/addressbook/backends/file/e-book-backend-file.c b/addressbook/backends/file/e-book-backend-file.c
index b86384c..a0a35bd 100644 (file)
--- a/addressbook/backends/file/e-book-backend-file.c
+++ b/addressbook/backends/file/e-book-backend-file.c
@@ -652,8 +652,8 @@ e_book_backend_file_load_revision (EBookBackendFile *bf)
                                                   &error)) {
                g_warning (
                        G_STRLOC ": Error loading database revision: %s",
-                       error->message);
-               g_error_free (error);
+                       error ? error->message : "Unknown error");
+               g_clear_error (&error);
        } else if (bf->priv->revision == NULL) {
                e_book_backend_file_bump_revision (bf);
        }
@@ -1455,17 +1455,18 @@ e_book_backend_file_open (EBookBackendSync *backend,
                return;
        bf->priv->photo_dirname = dirname;
 
-       e_book_backend_file_load_revision (bf);
+       g_rec_mutex_lock (&bf->priv->revision_mutex);
+       if (!bf->priv->revision) {
+               e_book_backend_file_load_revision (bf);
+               e_book_backend_notify_property_changed (E_BOOK_BACKEND (backend),
+                                                       BOOK_BACKEND_PROPERTY_REVISION,
+                                                       bf->priv->revision);
+               g_rec_mutex_unlock (&bf->priv->revision_mutex);
+       }
 
        e_book_backend_notify_online (E_BOOK_BACKEND (backend), TRUE);
        e_book_backend_notify_readonly (E_BOOK_BACKEND (backend), FALSE);
        e_book_backend_notify_opened (E_BOOK_BACKEND (backend), NULL /* Success */);
-
-       g_rec_mutex_lock (&bf->priv->revision_mutex);
-       e_book_backend_notify_property_changed (E_BOOK_BACKEND (backend),
-                                               BOOK_BACKEND_PROPERTY_REVISION,
-                                               bf->priv->revision);
-       g_rec_mutex_unlock (&bf->priv->revision_mutex);
 }
 
 static gboolean