same problem on master with SpamBlacklist + Wikibase.

[d9c87ae3] /wiki/Special:NewItem Exception from line 117 of /Library/WebServer/Documents/wikidata/includes/WikiPage.php: Invalid or virtual namespace -1 given.
Backtrace:
#0 /Library/WebServer/Documents/wikidata/includes/context/RequestContext.php(200): WikiPage::factory(Title)
#1 /Library/WebServer/Documents/wikidata/extensions/SpamBlacklist/SpamBlacklistHooks.php(28): RequestContext->getWikiPage()
#2 [internal function]: SpamBlacklistHooks::filterMergedContent(RequestContext, Wikibase\ItemContent, Status, string, User, boolean)
#3 /Library/WebServer/Documents/wikidata/includes/Hooks.php(199): call_user_func_array(string, array)
#4 /Library/WebServer/Documents/wikidata/includes/GlobalFunctions.php(4032): Hooks::run(string, array)
#5 /Library/WebServer/Documents/wikidata/extensions/Wikibase/repo/includes/EditEntity.php(685): wfRunHooks(string, array)
#6 /Library/WebServer/Documents/wikidata/extensions/Wikibase/repo/includes/specials/SpecialNewEntity.php(103): Wikibase\EditEntity->attemptSave(string, integer, string)
#7 /Library/WebServer/Documents/wikidata/includes/specialpage/SpecialPage.php(374): Wikibase\Repo\Specials\SpecialNewEntity->execute(NULL)
#8 /Library/WebServer/Documents/wikidata/includes/SpecialPageFactory.php(487): SpecialPage->run(NULL)
#9 /Library/WebServer/Documents/wikidata/includes/Wiki.php(298): SpecialPageFactory::executePath(Title, RequestContext)
#10 /Library/WebServer/Documents/wikidata/includes/Wiki.php(599): MediaWiki->performRequest()
#11 /Library/WebServer/Documents/wikidata/includes/Wiki.php(460): MediaWiki->main()
#12 /Library/WebServer/Documents/wikidata/index.php(49): MediaWiki->run()
#13 {main}

Version: master
Severity: normal