"Firefox Screenshots went haywire" on a particular page - TypeError: event.target.getElementsByClassName(...)[i] is undefined

[pfctdayelise]

Steps to reproduce

1. Go to http://www.vafa.com.au/sections/womens-football/
2. Click the three dots, 'Take a Screenshot'

Expected: Get the "Drag or click on the page to selection a region" overlay. 'Save full page' and 'Save visible' overlay buttons should be clickable.

Actual: The overlay appears but is covered by another overlay with the close/copy/download buttons. On moving the mouse I immediately get the 'went haywire' dialog and a unhandled error in the developer tools console.

I am able to use 'Take a Screenshot' on other pages so perhaps it is something about this webpage.

In the console:

Unhandled error: TypeError: "event.target.getElementsByClassName(...)[i] is undefined"
	mousemove moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/selector/uicontrol.js:355:11
	fn moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/selector/uicontrol.js:852:36
	assertIsTrusted moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/assertIsTrusted.js:17:12
	catcher moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/catcher.js:55:16
	catcher moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/catcher.js:55:16
 undefined catcher.js:17:7
	exports.unhandled moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/catcher.js:17:7
	watchFunction/this.catcher moz-extension://744d91c3-801a-4af1-b0d3-258b185817a3/catcher.js:58:11

The line in uicontrol.js is: event.target.getElementsByClassName("eyeball")[i].style.transform = move;

I have attached two screenshots as well.

Config info: Firefox 64.0 Build number 20181207224003 Firefox Screenshots 35.0.0 OS Linux 4.15.0-42-generic (Ubuntu 18.04)

Before mouse move:

After mouse move:

[SoftVision-CosminMuntean]

@pfctdayelise thanks for reporting this! I have managed to reproduce the issue on latest Firefox 64.0 release and latest Nightly 66.0a1 build on Windows 7x64, Mac 10.13 and Ubuntu 18.04.

It seems that this issue is also reproducible on https://internshala.com/ website.

[vlna]

Same issue at https://ec.europa.eu/eures/public/sk/homepage - Windows Firefox 66.0.5 (64 bit)