'TypeError: counterItem is null' if no HTTPS-Everywhere button is in the toolbar
I get the exception mentioned in the summary when starting Tor Browser 4 (which does not have the HTTPS-Everyhwere toolbar button on the toolbar anymore). The offending line in question is:
counterItem.setAttribute('checked', showCounter ? 'true' : 'false');
Should be a matter of a try-catch that is missing here I guess as HTTPS-Everywhere is still working as expected.