Change (fb8d0b07) introduces the use of Title::castFromPageIdentity which is available from 1.36+.
When viewing diffs from pages with approved revisions while being on <1.36, this causes the following exception:
[f6a1a16f20967c7a94dd6269] /index.php?title=...&diff=next&oldid=61329 Error from line 966 undefined method Title::castFromPageIdentity()
Backtrace:
#0 /var/www/html/includes/HookContainer/HookContainer.php(329): ApprovedRevsHooks::addApprovalDiffLink(MediaWiki\Revision\RevisionStoreRecord, array, MediaWiki\Revision...
#1 /var/www/html/includes/HookContainer/HookContainer.php(132): MediaWiki\HookContainer\HookContainer->callLegacyHook(string, array, array, array)
#2 /var/www/html/includes/HookContainer/HookRunner.php(1499): MediaWiki\HookContainer\HookContainer->run(string, array)
#3 /var/www/html/includes/diff/DifferenceEngine.php(791): MediaWiki\HookContainer\HookRunner->onDiffTools(MediaWiki\Revision\RevisionStoreRecord, array, MediaWiki\Revision\RevisionStoreRecord, User)
#4 /var/www/html/includes/page/Article.php(986): DifferenceEngine->showDiffPage(boolean)
#5 /var/www/html/includes/page/Article.php(662): Article->showDiffPage()
#6 /var/www/html/includes/actions/ViewAction.php(74): Article->view()
#7 /var/www/html/includes/MediaWiki.php(527): ViewAction->show()
#8 /var/www/html/includes/MediaWiki.php(313): MediaWiki->performAction(Article, Title)
#9 /var/www/html/includes/MediaWiki.php(940): MediaWiki->performRequest()
#10 /var/www/html/includes/MediaWiki.php(543): MediaWiki->main()
#11 /var/www/html/index.php(53): MediaWiki->run()
#12 /var/www/html/index.php(46): wfIndexMain()
#13 {main}