MediaWiki internal error.

Original exception: [ZcW2sTbp2-YvAAyMOj_HSwAAAXI] /wiki/User:FlashGordon Error: Call to undefined method MediaWiki\User\User::idFromName()
Backtrace:
from /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(232)
#0 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(344): Conditions->isForeignUserPage(MediaWiki\Title\Title)
#1 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(254): Conditions->testCondition(integer, boolean, array)
#2 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(2529): Conditions->testConditions(array, array)
#3 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(2566): Hierarchy->updateTreeviewState_r(array)
#4 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(291): Hierarchy->updateTreeviewState_r(array)
#5 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(449): Hierarchy->getCurrentHierarchy()
#6 /home2/laird/www/clc-wiki.net/mediawiki/skins/Treeview/Treeview.php(127): Hierarchy->buildHierarchyHtml()
#7 /home2/laird/www/clc-wiki.net/mediawiki/skins/Treeview/Treeview.php(590): SkinTreeview->outputPage_ex(TreeviewTemplate)
#8 /home2/laird/www/clc-wiki.net/mediawiki/includes/skins/SkinTemplate.php(148): TreeviewTemplate->execute()
#9 /home2/laird/www/clc-wiki.net/mediawiki/includes/skins/SkinTemplate.php(174): SkinTemplate->generateHTML()
#10 /home2/laird/www/clc-wiki.net/mediawiki/includes/Output/OutputPage.php(2947): SkinTemplate->outputPage()
#11 /home2/laird/www/clc-wiki.net/mediawiki/includes/MediaWiki.php(978): MediaWiki\Output\OutputPage->output(boolean)
#12 /home2/laird/www/clc-wiki.net/mediawiki/includes/MediaWiki.php(613): MediaWiki->main()
#13 /home2/laird/www/clc-wiki.net/mediawiki/index.php(50): MediaWiki->run()
#14 /home2/laird/www/clc-wiki.net/mediawiki/index.php(46): wfIndexMain()
#15 {main}

Exception caught inside exception handler: [ZcW2sTbp2-YvAAyMOj_HSwAAAXI] /wiki/User:FlashGordon Error: Call to undefined method MediaWiki\User\User::idFromName()
Backtrace:
from /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(232)
#0 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(344): Conditions->isForeignUserPage(MediaWiki\Title\Title)
#1 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Conditions.php(254): Conditions->testCondition(integer, boolean, array)
#2 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(2529): Conditions->testConditions(array, array)
#3 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(2566): Hierarchy->updateTreeviewState_r(array)
#4 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(291): Hierarchy->updateTreeviewState_r(array)
#5 /home2/laird/www/clc-wiki.net/mediawiki/extensions/Hierarchy/Hierarchy.php(449): Hierarchy->getCurrentHierarchy()
#6 /home2/laird/www/clc-wiki.net/mediawiki/skins/Treeview/Treeview.php(127): Hierarchy->buildHierarchyHtml()
#7 /home2/laird/www/clc-wiki.net/mediawiki/skins/Treeview/Treeview.php(590): SkinTreeview->outputPage_ex(TreeviewTemplate)
#8 /home2/laird/www/clc-wiki.net/mediawiki/includes/skins/SkinTemplate.php(148): TreeviewTemplate->execute()
#9 /home2/laird/www/clc-wiki.net/mediawiki/includes/skins/SkinTemplate.php(174): SkinTemplate->generateHTML()
#10 /home2/laird/www/clc-wiki.net/mediawiki/includes/Output/OutputPage.php(2947): SkinTemplate->outputPage()
#11 /home2/laird/www/clc-wiki.net/mediawiki/includes/exception/MWExceptionRenderer.php(188): MediaWiki\Output\OutputPage->output()
#12 /home2/laird/www/clc-wiki.net/mediawiki/includes/exception/MWExceptionRenderer.php(105): MWExceptionRenderer::reportHTML(Error)
#13 /home2/laird/www/clc-wiki.net/mediawiki/includes/exception/MWExceptionHandler.php(134): MWExceptionRenderer::output(Error, integer)
#14 /home2/laird/www/clc-wiki.net/mediawiki/includes/exception/MWExceptionHandler.php(251): MWExceptionHandler::report(Error)
#15 /home2/laird/www/clc-wiki.net/mediawiki/includes/MediaWiki.php(635): MWExceptionHandler::handleException(Error, string)
#16 /home2/laird/www/clc-wiki.net/mediawiki/index.php(50): MediaWiki->run()
#17 /home2/laird/www/clc-wiki.net/mediawiki/index.php(46): wfIndexMain()
#18 {main}