Spotted in production:
Invalid or virtual namespace -1 given.
On urls of the format:
/w/api.php?action=flow&format=json&submodule=view-header&uselang=en&page=Special%3AUndelete&vhformat=html
With the following stacktrace:
#0 /srv/mediawiki/php-1.30.0-wmf.17/extensions/Flow/includes/WorkflowLoaderFactory.php(76): WikiPage::factory(Title) #1 /srv/mediawiki/php-1.30.0-wmf.17/extensions/Flow/includes/Api/ApiFlowBase.php(78): Flow\WorkflowLoaderFactory->createWorkflowLoader(Title) #2 /srv/mediawiki/php-1.30.0-wmf.17/extensions/Flow/includes/Api/ApiFlowBaseGet.php(12): Flow\Api\ApiFlowBase->getLoader() #3 /srv/mediawiki/php-1.30.0-wmf.17/extensions/Flow/includes/Api/ApiFlow.php(100): Flow\Api\ApiFlowBaseGet->execute() #4 /srv/mediawiki/php-1.30.0-wmf.17/includes/api/ApiMain.php(1583): Flow\Api\ApiFlow->execute() #5 /srv/mediawiki/php-1.30.0-wmf.17/includes/api/ApiMain.php(546): ApiMain->executeAction() #6 /srv/mediawiki/php-1.30.0-wmf.17/includes/api/ApiMain.php(517): ApiMain->executeActionWithErrorHandling() #7 /srv/mediawiki/php-1.30.0-wmf.17/api.php(94): ApiMain->execute() #8 /srv/mediawiki/w/api.php(3): include(string) #9 {main}