matplotlib/matplotlib — pull request #2648 by JamesMakela (2013-12-04 19:45:38+00:00)
Title: Update backend_webagg.py

Change WebAgg backend to handle stale figure UI controls in the browser
---------------
I found that when you create a figure, render it in a browser, and then close the figure, it leaves a UI in the browser with no associated figure on the server. This UI is still handling mouse cursor events and sending them, which was causing some annoying exceptions due to the backend trying to perform operations with an invalid fig_manager.