Error from line 27 of /var/www/html/w/extensions/DocBookExport/DocBookExport.php: Call to a member function getText() on null
Backtrace:
#0 /var/www/html/w/extensions/DocBookExport/DocBookExport.php(13): DocBookExport::parseDocBookSyntax(Parser, array)
#1 /var/www/html/w/includes/parser/Parser.php(3383): DocBookExport::parseDocBookSyntaxParserFunction(Parser, string, string, string)
#2 /var/www/html/w/includes/parser/Parser.php(3106): Parser->callParserFunction(PPFrame_DOM, string, array)
#3 /var/www/html/w/includes/parser/Preprocessor_DOM.php(1229): Parser->braceSubstitution(array, PPFrame_DOM)
#4 /var/www/html/w/includes/parser/Parser.php(2921): PPFrame_DOM->expand(DOMElement, integer)
#5 /var/www/html/w/includes/parser/Parser.php(1277): Parser->replaceVariables(string)
#6 /var/www/html/w/includes/parser/Parser.php(451): Parser->internalParse(string)
#7 /var/www/html/w/includes/StubObject.php(111): Parser->parse(string, Title, ParserOptions, boolean, boolean, integer)
#8 /var/www/html/w/includes/StubObject.php(137): StubObject->_call(string, array)
#9 /var/www/html/w/includes/content/WikitextContent.php(329): StubObject->__call(string, array)
#10 /var/www/html/w/includes/content/AbstractContent.php(516): WikitextContent->fillParserOutput(Title, integer, ParserOptions, boolean, ParserOutput)
#11 /var/www/html/w/includes/jobqueue/jobs/RefreshLinksJob.php(227): AbstractContent->getParserOutput(Title, integer, ParserOptions, boolean)
#12 /var/www/html/w/includes/jobqueue/jobs/RefreshLinksJob.php(122): RefreshLinksJob->runForTitle(Title)
#13 /var/www/html/w/includes/jobqueue/JobRunner.php(295): RefreshLinksJob->run()
#14 /var/www/html/w/includes/jobqueue/JobRunner.php(193): JobRunner->executeJob(RefreshLinksJob, Wikimedia\Rdbms\LBFactorySimple, BufferingStatsdDataFactory, integer)
#15 /var/www/html/w/maintenance/runJobs.php(86): JobRunner->run(array)
#16 /var/www/html/w/maintenance/doMaintenance.php(92): RunJobs->execute()
#17 /var/www/html/w/maintenance/runJobs.php(119): require_once(string)
#18 {main}