```name=Error
ParameterAssertionException: Bad value for parameter $title: invalid name 'Beiträge/Alex
_Alex_Lep'
```
```name=exception.trace,lines=12
from /srv/mediawiki/php-1.35.0-wmf.16/vendor/wikimedia/assert/src/Assert.php:70
#0 /srv/mediawiki/php-1.35.0-wmf.16/includes/title/TitleValue.php(157): Wikimedia\Assert\Assert::parameter(boolean, string, string)
#1 /srv/mediawiki/php-1.35.0-wmf.16/includes/title/TitleValue.php(121): TitleValue::assertValidSpec(integer, string, string, string)
#2 /srv/mediawiki/php-1.35.0-wmf.16/includes/specialpage/SpecialPage.php(102): TitleValue->__construct(integer, string, string)
#3 /srv/mediawiki/php-1.35.0-wmf.16/includes/specialpage/SpecialPage.php(85): SpecialPage::getTitleValueFor(string, string, string)
#4 /srv/mediawiki/php-1.35.0-wmf.16/includes/user/ExternalUserNames.php(79): SpecialPage::getTitleFor(string, string)
#5 /srv/mediawiki/php-1.35.0-wmf.16/includes/Linker.php(909): ExternalUserNames::getUserLinkTitle(string)
#6 /srv/mediawiki/php-1.35.0-wmf.16/includes/Linker.php(1132): Linker::userLink(integer, string)
#7 /srv/mediawiki/php-1.35.0-wmf.16/includes/diff/DifferenceEngine.php(746): Linker::revUserTools(Revision, boolean)
#8 /srv/mediawiki/php-1.35.0-wmf.16/includes/page/Article.php(965): DifferenceEngine->showDiffPage(boolean)
#9 /srv/mediawiki/php-1.35.0-wmf.16/includes/page/Article.php(643): Article->showDiffPage()
#10 /srv/mediawiki/php-1.35.0-wmf.16/includes/actions/ViewAction.php(63): Article->view()
#11 /srv/mediawiki/php-1.35.0-wmf.16/includes/MediaWiki.php(514): ViewAction->show()
#12 /srv/mediawiki/php-1.35.0-wmf.16/includes/MediaWiki.php(304): MediaWiki->performAction(Article, Title)
#13 /srv/mediawiki/php-1.35.0-wmf.16/includes/MediaWiki.php(967): MediaWiki->performRequest()
#14 /srv/mediawiki/php-1.35.0-wmf.16/includes/MediaWiki.php(530): MediaWiki->main()
#15 /srv/mediawiki/php-1.35.0-wmf.16/index.php(46): MediaWiki->run()
#16 /srv/mediawiki/w/index.php(3): require(string)
#17 {main}
```
### Notes
In dewiki, I am getting a couple of exceptions that make diffs and (partially) page histories inaccesible, e.g. `[XjvqYgpAMFAAAH7XbeYAAABH] 2020-02-06 10:28:51: Fatal exception of type "Wikimedia\Assert\ParameterAssertionException"`.
I stumbled upon this when doing queries on the dewiki `actor_revision` table, in which the row with `actor_id=10630425` has a weird `actor_name` that just seems to be broken. Turns out that I get a `Wikimedia\Assert\ParameterAssertionException` when trying to access the three diffs that this actor made, or when accessing the corresponding page histories.
Quick links to diffs and histories that yield this exception:
* https://de.wikipedia.org/w/index.php?diff=130476910 and https://de.wikipedia.org/w/index.php?diff=130477420 on page https://de.wikipedia.org/w/index.php?title=S%C5%BDD-Baureihe_%D0%A4%D0%94&offset=20100102120249&action=history
* https://de.wikipedia.org/w/index.php?diff=130473547 on page https://de.wikipedia.org/w/index.php?title=S%C5%BDD-Baureihe_%D0%9B%D0%92&action=history
All diffs stem from imports from ruwiki to dewiki.