Sometimes it display the following message and please fix it.

MediaWiki internal error.

Original exception: exception 'MWException' with message 'PPFrame_DOM::expand: Invalid parameter type' in /usr/local/apache/common-local/wmf-deployment/includes/parser/Preprocessor_DOM.php:1056
Stack trace:
#0 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(2733): PPFrame_DOM->expand(Object(PPNode_DOM), 0)
#1 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(935): Parser->replaceVariables('{{Main page hea...')
#2 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(335): Parser->internalParse('{{Main page hea...')
#3 [internal function]: Parser->parse('{{Main page hea...', Object(Title), Object(ParserOptions), true, true, 67084)
#4 /usr/local/apache/common-local/wmf-deployment/includes/StubObject.php(58): call_user_func_array(Array, Array)
#5 /usr/local/apache/common-local/wmf-deployment/includes/StubObject.php(76): StubObject->_call('parse', Array)
#6 [internal function]: StubObject->__call('parse', Array)
#7 /usr/local/apache/common-local/wmf-deployment/includes/Article.php(4024): StubObject->parse('{{Main page hea...', Object(Title), Object(ParserOptions), true, true, 67084)
#8 /usr/local/apache/common-local/wmf-deployment/includes/Article.php(4006): Article->getOutputFromWikitext('{{Main page hea...', true, Object(ParserOptions))
#9 /usr/local/apache/common-local/wmf-deployment/includes/Article.php(1349): Article->outputWikiText('{{Main page hea...', true, Object(ParserOptions))
#10 [internal function]: Article->doViewParse()
#11 /usr/local/apache/common-local/wmf-deployment/includes/PoolCounter.php(59): call_user_func(Array)
#12 /usr/local/apache/common-local/wmf-deployment/includes/Article.php(904): PoolCounter_Stub->executeProtected(Array, Array)
#13 /usr/local/apache/common-local/wmf-deployment/includes/Wiki.php(493): Article->view()
#14 /usr/local/apache/common-local/wmf-deployment/includes/Wiki.php(70): MediaWiki->performAction(Object(OutputPage), Object(Article), Object(Title), Object(User), Object(WebRequest))
#15 /usr/local/apache/common-local/wmf-deployment/index.php(117): MediaWiki->performRequestForTitle(Object(Title), Object(Article), Object(OutputPage), Object(User), Object(WebRequest))
#16 /usr/local/apache/common-local/live-1.5/index.php(3): require('/usr/local/apac...')
#17 {main}

Exception caught inside exception handler: exception 'MWException' with message 'PPFrame_DOM::expand: Invalid parameter type' in /usr/local/apache/common-local/wmf-deployment/includes/parser/Preprocessor_DOM.php:1056
Stack trace:
#0 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(2733): PPFrame_DOM->expand(Object(PPNode_DOM), 0)
#1 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(518): Parser->replaceVariables('{{SITENAME}} ({...')
#2 /usr/local/apache/common-local/wmf-deployment/includes/parser/Parser.php(4194): Parser->preprocess('{{SITENAME}} ({...', Object(Title), Object(ParserOptions))
#3 /usr/local/apache/common-local/wmf-deployment/includes/MessageCache.php(674): Parser->transformMsg('{{SITENAME}} ({...', Object(ParserOptions))
#4 /usr/local/apache/common-local/wmf-deployment/includes/GlobalFunctions.php(744): MessageCache->transform('{{SITENAME}} ({...')
#5 /usr/local/apache/common-local/wmf-deployment/includes/GlobalFunctions.php(707): wfMsgGetKey('opensearch-desc', true, true, true)
#6 /usr/local/apache/common-local/wmf-deployment/includes/GlobalFunctions.php(655): wfMsgReal('opensearch-desc', Array, true, true)
#7 /usr/local/apache/common-local/wmf-deployment/includes/Skin.php(203): wfMsgForContent('opensearch-desc')
#8 /usr/local/apache/common-local/wmf-deployment/skins/Vector.php(31): Skin->initPage(Object(OutputPage))
#9 /usr/local/apache/common-local/wmf-deployment/includes/SkinTemplate.php(146): SkinVector->initPage(Object(OutputPage))
#10 /usr/local/apache/common-local/wmf-deployment/includes/OutputPage.php(1559): SkinTemplate->outputPage(Object(OutputPage))
#11 /usr/local/apache/common-local/wmf-deployment/includes/Exception.php(164): OutputPage->output()
#12 /usr/local/apache/common-local/wmf-deployment/includes/Exception.php(191): MWException->reportHTML()
#13 /usr/local/apache/common-local/wmf-deployment/includes/Exception.php(289): MWException->report()
#14 /usr/local/apache/common-local/wmf-deployment/includes/Exception.php(348): wfReportException(Object(MWException))
#15 [internal function]: wfExceptionHandler(Object(MWException))
#16 {main}

Version: unspecified
Severity: enhancement
URL: http://http://zh.wikinews.org