In production logs. 331 errors in the last hour. New error in 1.41.0-wmf.5 . Impacts logged in users on certain browsers.
Also appears as InvalidCharacterError: DOMTokenList.add: The token can not contain whitespace.
```
at https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:355:510
at Object.fire https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:287:808
at ULS.onVisible https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:125:878
at ULS.visible <anonymous>:20:691
at ULS.show <anonymous>:21:450
at ULS.click <anonymous>:24:50
at HTMLButtonElement.dispatch https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:201:260
at elemData.handle https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:197:877
at Object.trigger https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:247:983
at HTMLButtonElement.<anonymous> https://en.wikipedia.org/w/load.php?lang=en&modules=ext.echo.api%7Cext.eventLogging%2CnavigationTiming%2CwikimediaEvents%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.interface%7Cjquery%7Cjquery.makeCollapsible%7Cmediawiki.base%2Cexperiments%2Cutil%7Cmediawiki.page.watch.ajax%7Coojs-ui.styles.icons-interactions%7Cskins.vector.icons.js%7Cskins.vector.js&skin=vector-2022&version=1usc1:248:961
```
== QA steps
1) Login and visit https://en.wikipedia.org/wiki/Barack_Obama in Chrome
2) Open the devtools console
3) Click the ULS button
4) Verify that ULS opens and that there is not an error in the console
5) While the ULS dialog is open, scroll down the page.
6) Verify that the sticky header appears