Synchronize all for receiving folders only

app/src/main/java/eu/faircode/email/AdapterFolder.java

@@ -350,9 +350,10 @@ public class AdapterFolder extends RecyclerView.Adapter<AdapterFolder.ViewHolder
             popupMenu.getMenu().add(Menu.NONE, 0, 0, folder.getDisplayName(context)).setEnabled(false);
 
             popupMenu.getMenu().add(Menu.NONE, R.string.title_synchronize_now, 1, R.string.title_synchronize_now);
-            popupMenu.getMenu().add(Menu.NONE, R.string.title_synchronize_all, 2, R.string.title_synchronize_all);
 
             if (folder.account != null) {
+                popupMenu.getMenu().add(Menu.NONE, R.string.title_synchronize_all, 2, R.string.title_synchronize_all);
+
                 SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
                 String startup = prefs.getString("startup", "unified");
                 if (!"accounts".equals(startup))