When adding events by clicking the calendar portlet or moving events on the portlet, the "Your request completed successfully" pop-ups appear, but are invisible and do not get cleared. If you create enough events, they begin to cover parts of the portlet, making it unusable.
Steps to Reproduce:
1. Add a Calendar portlet to any page.
2. Add an event.
3. Move the event (to change it). Observe success pop-ups appearing.
4. Repeat #3 until you cannot click the event anymore.
5. Note you cannot click any buttons above the event either.
The alert wrappers should not be permanent / inhibit functionality.
The invisible wrappers cover the portlet and break its usability.
Issue reproduced in branch.
Issue reproduced in master