Spotted while switching the beta cluster over from using the Wikidata build to master of the extensions.
They are not related to the build.
I believe I produced these by making a new item, and then loading recent changes on either a client or repo.
[{exception_id}] {exception_url} ErrorException from line 73 of /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php: PHP Warning: get_class() expects parameter 1 to be object, string given
[{exception_id}] {exception_url} ErrorException from line 309 of /srv/mediawiki-staging/php-master/includes/debug/MWDebug.php: PHP Warning: Cannot get sitelink diff from . Change #1371937, type wikibase-item~add [Called from Wikibase\ItemChange::logWarn/srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php:73
PHP Warning: get_class() expects parameter 1 to be object, string given
#0 [internal function]: MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php(73): get_class(string)
#2 /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php(32): Wikibase\ItemChange->logWarning(string)
#3 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(346): Wikibase\ItemChange->getSiteLinkDiff()
#4 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(405): Wikibase\Repo\ChangeDispatcher->isRelevantChange(Wikibase\ItemChange, string)
#5 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(315): Wikibase\Repo\ChangeDispatcher->filterChanges(string, array, integer)
#6 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(234): Wikibase\Repo\ChangeDispatcher->getPendingChanges(string, integer)
#7 /srv/mediawiki-staging/php-master/extensions/Wikidata/extensions/Wikibase/repo/maintenance/dispatchChanges.php(272): Wikibase\Repo\ChangeDispatcher->dispatchTo(array)
#8 /srv/mediawiki-staging/php-master/maintenance/doMaintenance.php(95): Wikibase\DispatchChanges->execute()
#9 /srv/mediawiki-staging/php-master/extensions/Wikidata/extensions/Wikibase/repo/maintenance/dispatchChanges.php(366): require_once(string)
#10 /srv/mediawiki-staging/multiversion/MWScript.php(100): require_once(string)
#11 {main}/srv/mediawiki-staging/php-master/includes/debug/MWDebug.php:309
PHP Warning: Cannot get sitelink diff from . Change #1371938, type wikibase-item~update [Called from Wikibase\ItemChange::logWarning in /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php at line 76]
#0 [internal function]: MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /srv/mediawiki-staging/php-master/includes/debug/MWDebug.php(309): trigger_error(string, integer)
#2 /srv/mediawiki-staging/php-master/includes/debug/MWDebug.php(164): MWDebug::sendMessage(string, array, string, integer)
#3 /srv/mediawiki-staging/php-master/includes/GlobalFunctions.php(1209): MWDebug::warning(string, integer, integer, string)
#4 /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php(76): wfLogWarning(string)
#5 /srv/mediawiki-staging/php-master/extensions/Wikibase/lib/includes/Changes/ItemChange.php(32): Wikibase\ItemChange->logWarning(string)
#6 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(346): Wikibase\ItemChange->getSiteLinkDiff()
#7 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(405): Wikibase\Repo\ChangeDispatcher->isRelevantChange(Wikibase\ItemChange, string)
#8 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(315): Wikibase\Repo\ChangeDispatcher->filterChanges(string, array, integer)
#9 /srv/mediawiki-staging/php-master/extensions/Wikibase/repo/includes/ChangeDispatcher.php(234): Wikibase\Repo\ChangeDispatcher->getPendingChanges(string, integer)
#10 /srv/mediawiki-staging/php-master/extensions/Wikidata/extensions/Wikibase/repo/maintenance/dispatchChanges.php(272): Wikibase\Repo\ChangeDispatcher->dispatchTo(array)
#11 /srv/mediawiki-staging/php-master/maintenance/doMaintenance.php(95): Wikibase\DispatchChanges->execute()
#12 /srv/mediawiki-staging/php-master/extensions/Wikidata/extensions/Wikibase/repo/maintenance/dispatchChanges.php(366): require_once(string)
#13 /srv/mediawiki-staging/multiversion/MWScript.php(100): require_once(string)
#14 {main}https://logstash-beta.wmflabs.org/goto/e59b90150ba02964f4c36a3555987f6e