When you receive meeting invites on an account that doesn't have a calendar, you can specify a calendar where you accept the invite.

1.) Tap on More (...) in the lower right of your screen on mobile (iOS/Android) and lower left on cloze.com.


2.) Tap on Settings


3.) Tap on Mail Settings to expand the section and then scroll down to the section a labeled "Meeting Invites". 

4.) Tap on the dropdown in the Meeting Invites section to set a default calendar.