Ghostery locks up Firefox for Android if its "Page not scanned" dialog appears

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I'm using Firefox for Android 37.0.2 on a 2013 Moto X running KitKat. Because of the awful positioning of the Ghostery 5.4.3 icon (see "Ghostery button on Firefox for Android" topic), I often accidentally activate Ghostery with my thumb when trying to scroll. Usually when I do so the full-size Ghostery dialog shows "Ghostery found N trackers" and I can click its white X in the top-left to dismiss and get back to the browser tab

Other times I'll trigger
[JavaScript Application]
Remov Ghostery's button?
(To permanently remove it, go to Ghostery's Options.)
and I'll click OK and get back to the browser tab.

But sometimes the full-size Ghostery dialog shows (see screenshot below)
Page not scanned
This page was not scanned.
Ghostery only scans "http" and "https" pages, and only pages loaded after Ghostery was installed.

For some reason in this scenario the white x in the top-left is inactive, even though it looks exactly like the first scenario, and I can't close the dialog no matter how carefully I target the white X. At this point I am f***ed. I can't swipe in any direction to get back to Firefox's set of tabs. Rotating the screen, power-off and -on, pinch/zoom gestures, clicking the [gear], [Pause Blocking], [Whitelist Site], [?] icons do not make the dialog go away, and it's full-screen blocking everything below it. I don't know how to bring up a keyboard, and even if I did, there's no [Escape] key to press.

My only option is to get to Android's list of running apps, press and hold on Firefox, choose App info, and choose Remove from List or Force stop, losing all my work in all my tabs.
This is terrible!

The only other Firefox Android addons I run are AdBlock Plus 2.6.9, and the OpenH265 Video Codec 1.3 and Privacy Coach 1.2 that came with Firefox for Android.