In that function, it calls $this->loadText() to load text. In loadText(), it calls self::getRevisionText() and it's said to "@return String: text the text requested or false on failure". When loading of text fails, loadText() returns false, then false is passed to $handler->unserializeContent(), causing exception "TextContent expects a string in the constructor."
TextContent expects a string in the constructor.
Backtrace:
#0 /home/liangent/code/gerrit/mediawiki/core/includes/content/WikitextContent.php(8): TextContent->construct(false, 'wikitext')
#1 /home/liangent/code/gerrit/mediawiki/core/includes/content/ContentHandler.php(1185): WikitextContent->construct(false)
#2 /home/liangent/code/gerrit/mediawiki/core/includes/Revision.php(979): WikitextContentHandler->unserializeContent(false, 'text/x-wiki')
#3 /home/liangent/code/gerrit/mediawiki/core/includes/Revision.php(921): Revision->getContentInternal()
#4 /home/liangent/code/gerrit/mediawiki/core/includes/Revision.php(897): Revision->getContent(1, NULL)
#5 /home/liangent/code/gerrit/mediawiki/core/extensions/Wikipedia/classes/WikipediaHooks.php(273): Revision->getText()
...
Version: unspecified
Severity: normal