Vague console error when clicking 'X' buttons to close the screenshots UI (webextension version).

[wisniewskit]

While clicking the 'X' cancel buttons on the webextension version of screenshots, I see this error logged in the browser console:

TypeError: window is null; can't access its "parent" property

This occurs in the following Firefox code in WebNavigationFrames.jsm:

function getFrameId(window) {
  if (window.parent === window) {
    return 0;
  }

  let utils = window.windowUtils;
  return utils.outerWindowID;
}

Presumably this may be happening because the screenshots iframe is being removed while or before other code is trying to access via some extension API call, but I have not had time to investigate.

[johngruen]

@wisniewskit this is happening in nightly, yes. I think @6a68 should investigate next week when he's back