Remove call to Application.Current.Dispatcher.CheckAccess() - seems there's a null point happening on a rare instance when Application.Current.Dispatcher is null
Rely on parent calling code to execute on the correct thread (which it was already executing on the UI Thread)
Merge pull request #465 from amaitland/bug-fix/dispatcher-null-pointer

Remove call to Application.Current.Dispatcher.CheckAccess() - Fix null pointer when Application.Current is null