Yesterday I edited https://www.mediawiki.org/w/index.php?title=Manual%253ARunning_MediaWiki_on_macOS. After saving the edit in VE, I clicked on the edit link for section 9 and got this console error:
Uncaught TypeError: can't access property "items", this.actionsToolbar.getToolGroupByName(...) is null setupToolbarSaveButton https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:5 setupToolbar https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:427 setupToolbar https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:4 setSurface https://www.mediawiki.org/w/load.php?lang=en&modules=ext.visualEditor.base,core,diffing,mwsave,mwtransclusion&skin=vector-2022&version=1faib:21 setSurface https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:1054 setSurface https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:9 addSurface https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:1054 addSurface https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:3 setupSurface https://www.mediawiki.org/w/index.php?title=Manual:Running_MediaWiki_on_macOS&action=edit§ion=7 line 1256 > injectedScript:1053
The error went away after I reloaded the page.
I would expect the message to show up in mw-client-errors dashboard in Logstash, but I did not see it there.