Please describe the problem:
This is a serious usability problem - the calendar application asks a yes/no question: "Add the sender as an attendee?", but the dialog only offers an "OK" button where it clearly should have either OK/Cancel or Yes/No.

Steps to reproduce:
1. Send a meeting invitation to an alias of your primary mail account
2. when the meeting invitation is received, approve it using your primary mail address
3. when the approval arrives, click "update"


Actual results:
A dialog appears with a single OK button and no way to cancel the "add sender" action

Expected results:
The dialog that appears should have the option of canceling the add sender action

Does this happen every time?
yes

Other information:
A screenshot will be attached shortly