Event page detail page problems

I love the theme!

But my event detail page is strange…
When you go to:
https://nieuw.stalstonas.nl/nieuw/calendar/action~month/request_format~json/
And click on an event you see a first white space??
How is this possible.

It would be perfect when it comes in a pop-up
Just the same like you click on the widget on the home on an event:
https://nieuw.stalstonas.nl/nieuw/

I hope someone can help me! Thanks a lot!!