Notification from canceled event won't stop sending

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What steps will reproduce the problem?
1. I don't know
2.
3.

What is the expected output? What do you see instead?
The event should not send notifications.  Instead, all the invitees are 
receiving daily notifications.

What version of the product are you using? On what operating system?
Unsure what version -- On Mac OS X 10.8.5

Please provide any additional information below.

Hi Google, I created an event a long time ago, invited people, then I changed a 
detail about that event and sent out updates to the invitees, then the event 
happened, and I discovered that everybody that I'd invited, a month later, was 
still getting change notifications from when i'd updated the event.  I deleted 
the event, they continued to get the alert.  I cleared my cookies, my cache, 
disabled extensions, deleted everything on my calendar, they still get 
notifications every day (apparently multiple, sometimes!). 

Can you please help me?  It's going to 20-30 co-workers daily and is a huge 
professional embarrassment.  I don't want to stop using google calendar but if 
I can't get this resolved then I don't have faith that it won't happen again, 
and I'll have to move to Outlook.   Let me know if you need my calendar IDs and 
event IDs, I will send them in a private message.  Thank you!

Original issue reported on code.google.com by [email protected] on 29 Jul 2015 at 7:54