Firefox Nightly breaks HTTPS Everywhere UI

In the current Firefox Nightly (from 2013-08-01) there are two new UI problems: when starting the browser after installing HTTPS Everywhere for the first time, the SSL Observatory popup isn't dislayed; and the enable/disable rules toolbar icon doesn't show the number of active rules affecting the current page.

The second problem may be related to the following error on the console:

TypeError: alist.populate_list is not a function (in toolbar_button.js:142)

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