unpoly 3.8 error using browser back button

[hpvd]

First of all many thanks for this awesome piece of software! v3.8 would be worth a major version step :-)

Bug description

error on using browser back button.
possibly introduced with new features/changes of unpoly 3.8

Reproduction project

www.unpoly.com

Steps to reproduce the behavior:

1. Go to reproduction project linked above
2. Click in menu on 'passive updates'
3. Click in menu on 'up flashes'
4. Click browser back button
5. See error:

Uncaught up.: Cannot reveal a detached element
    <anonymous> https://unpoly.com/javascripts/guide-8c2112b3.js:29
    e https://unpoly.com/javascripts/guide-8c2112b3.js:29
    e https://unpoly.com/javascripts/guide-8c2112b3.js:33
    revealCurrent https://unpoly.com/javascripts/guide-8c2112b3.js:34
    r https://unpoly.com/javascripts/guide-8c2112b3.js:34
    revealCurrent https://unpoly.com/javascripts/guide-8c2112b3.js:34
    r https://unpoly.com/javascripts/guide-8c2112b3.js:34
    revealCurrent https://unpoly.com/javascripts/guide-8c2112b3.js:34
    r https://unpoly.com/javascripts/guide-8c2112b3.js:34
    l https://unpoly.com/javascripts/guide-8c2112b3.js:34
    setTimeout handler*te https://unpoly.com/javascripts/guide-8c2112b3.js:29
    l https://unpoly.com/javascripts/guide-8c2112b3.js:34
    setTimeout handler*te https://unpoly.com/javascripts/guide-8c2112b3.js:29
    c https://unpoly.com/javascripts/guide-8c2112b3.js:34
    nativeCallback https://unpoly.com/javascripts/guide-8c2112b3.js:30
    _dispatchEvent https://unpoly.com/javascripts/guide-8c2112b3.js:30
    emit https://unpoly.com/javascripts/guide-8c2112b3.js:30
    s https://unpoly.com/javascripts/guide-8c2112b3.js:32
    a https://unpoly.com/javascripts/guide-8c2112b3.js:33
    p https://unpoly.com/javascripts/guide-8c2112b3.js:33
    h https://unpoly.com/javascripts/guide-8c2112b3.js:33
    setTimeout handler*t</up.history< https://unpoly.com/javascripts/guide-8c2112b3.js:33
    nativeCallback https://unpoly.com/javascripts/guide-8c2112b3.js:30
    _dispatchEvent https://unpoly.com/javascripts/guide-8c2112b3.js:30
    emit https://unpoly.com/javascripts/guide-8c2112b3.js:30
    s https://unpoly.com/javascripts/guide-8c2112b3.js:32
    t https://unpoly.com/javascripts/guide-8c2112b3.js:32
    r https://unpoly.com/javascripts/guide-8c2112b3.js:32
    <anonymous> https://unpoly.com/javascripts/guide-8c2112b3.js:34
    <anonymous> https://unpoly.com/javascripts/guide-8c2112b3.js:34
[guide-8c2112b3.js:29:21724](https://unpoly.com/javascripts/guide-8c2112b3.js)

​

Expected behavior

no error

Browser version

• OS: [Windows]
• Browser [Firefox]
• Version [latest]

[hpvd]

[triskweline]

This is an issue in the unpoly.com site, not in Unpoly.