Error attempt to invoke virtual method

[voyteke]

I've installed the app, when I try to export my calendar with around 950 events app crashes with
Error attempt to invoke virtual method Long net fortuna ical4j model get time On null object reference

Screenshot attached

[MartinW42]

I too have this problem. Export was working until today when I added & changed several calendar entries. So I assume that one of these has a problem. Any ideas how I trace which one?