[epiphany] sync-service: Fix crash when signing out before the initial sync starts

[Gabriel Ivașcu <gabrielivascu src gnome org>]

commit b5bf5d6c64d2158dc835046d9efc14f07f817e74
Author: Gabriel Ivascu <gabrielivascu gnome org>
Date:   Mon May 7 01:00:34 2018 +0300

    sync-service: Fix crash when signing out before the initial sync starts

 lib/sync/ephy-sync-service.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/lib/sync/ephy-sync-service.c b/lib/sync/ephy-sync-service.c
index 5691df4..aa9cbe8 100644
--- a/lib/sync/ephy-sync-service.c
+++ b/lib/sync/ephy-sync-service.c
@@ -2797,9 +2797,10 @@ void
 ephy_sync_service_start_sync (EphySyncService *self)
 {
   g_assert (EPHY_IS_SYNC_SERVICE (self));
-  g_assert (ephy_sync_utils_user_is_signed_in ());
   g_assert (self->sync_periodically);
 
-  ephy_sync_service_sync_internal (self);
-  ephy_sync_service_schedule_periodical_sync (self);
+  if (ephy_sync_utils_user_is_signed_in ()) {
+    ephy_sync_service_sync_internal (self);
+    ephy_sync_service_schedule_periodical_sync (self);
+  }
 }