If you are an extension maintainer, or are interested in helping out, your help with the following task would be appreciated:
https://phabricator.wikimedia.org/T172146
As per T165149, the contract of Title::getTalkPage changes to throw an exception if called on a page in a namespace that does not have a talk namespace associated.
All calls to Title::getTalkPage must either be changed to getTalkPageIfDefined(), or they must first check canHaveTalkPage(). These checks can be omitted only for the User namespace, since user pages can always have talk pages. Note that some of the below may be calls to User::getTalkPage instead; those also don't need checks, since users can always have talk pages.
Offending calls to getTalkPage() should be removed from all extensions. They MUST be removed from all extensions deployed on the Wikimedia cluster before merging Icee208dc.
Below is a list of extensions with potentially offending calls to getTalkNamespace(). Please go through them, and tick them off in the phabricator task once the fix has been merged. If you made a patch bit it is not merged yet, you can link to it in the respective line of the task description.
[] ArticleComments [] ArticleFeedbackv5 [] BlueSpiceExtensions [] BlueSpiceFoundation [] CommentPages [] ConfirmAccount [] ConventionExtension [] DumpHTML [] Duplicator [] EditSubpages [] EducationProgram [] Favorites [] FlaggedRevs [] Flow [] GoogleNewsSitemap [] InterwikiIntegration [] LiquidThreads [] News [] ReaderFeedback [] WatchSubpages [] WikiLove [] WikibaseQualityConstraints [] Wikidata [] XMLContentExtension [] CologneBlue [] Nimbus [] Tempo
For a more detailed list, see the phabricator task.