==== What is the problem?
If I am on a wiki anonymously and without a temporary account and I attempt a [[https://www.mediawiki.org/wiki/Manual:Purge#Null_edits|null edit]], I see the below error:
```
[Y8gf6fZWmsIOsM8IfogQkwAAAAE] /w/index.php?action=submit&title=Lausanne MWException: Can't use the request user for storage with IP masking enabled
Backtrace:
from /srv/mediawiki/php-master/includes/EditPage.php(916)
#0 /srv/mediawiki/php-master/includes/EditPage.php(2764): EditPage->getUserForSave()
#1 /srv/mediawiki/php-master/includes/EditPage.php(2636): EditPage->updateWatchlist()
#2 /srv/mediawiki/php-master/includes/EditPage.php(1918): EditPage->internalAttemptSave(array, boolean, boolean)
#3 /srv/mediawiki/php-master/includes/EditPage.php(729): EditPage->attemptSave(array)
#4 /srv/mediawiki/php-master/includes/actions/EditAction.php(73): EditPage->edit()
#5 /srv/mediawiki/php-master/includes/actions/SubmitAction.php(38): EditAction->show()
#6 /srv/mediawiki/php-master/includes/MediaWiki.php(551): SubmitAction->show()
#7 /srv/mediawiki/php-master/includes/MediaWiki.php(328): MediaWiki->performAction(Article, Title)
#8 /srv/mediawiki/php-master/includes/MediaWiki.php(915): MediaWiki->performRequest()
#9 /srv/mediawiki/php-master/includes/MediaWiki.php(571): MediaWiki->main()
#10 /srv/mediawiki/php-master/index.php(50): MediaWiki->run()
#11 /srv/mediawiki/php-master/index.php(46): wfIndexMain()
#12 /srv/mediawiki/w/index.php(3): require(string)
#13 {main}
```
I can save an edit successfully if I modify the article before saving or if I already have a temporary account (or am logged in as a normal user).
==== Steps to reproduce problem
# Go to https://de.wikipedia.beta.wmflabs.org and check you don't already have a temporary account (if you do you will see a username in the top right such as `*Unregistered 1234`)
## If you do have a temporary account, clear your cookies or create a new browser profile or open a different browser
# Open the wikisource editor for any article (e.g. https://de.wikipedia.beta.wmflabs.org/w/index.php?title=Lausanne&action=edit)
# Do not change anything, just click Publish (or `Seite speichern`)
==== Environment
**Browser:** Firefox 91, 102
**Wiki(s):** https://de.wikipedia.beta.wmflabs.org MediaWiki 1.40.0-alpha (8080471) 11:01, 18 January 2023.