Browser console error "Invalid chrome URI: /" appears when opening extension prefs page

[aecreations]

Panic Button 4.1rc2

When opening the extension prefs page, the following error appears in the JavaScript console:

Invalid chrome URI: /

No line number is given.

This is caused by a known issue in Firefox when a page contains a password input field, i.e.<input type="password">. More info here: https://stackoverflow.com/questions/41744929/input-type-password-invalid-chrome-uri-firefox-only