TYPO3 Core

mod.linkvalidator {
    searchFields {
        pages = media,url
        tt_content = bodytext,header_link,records
        tt_news = bodytext,links
    }
    linktypes = db,file,external
    checkhidden = 0
    showCheckLinkTab = 1
    mail {
        fromname = Linkvalidator
        fromemail = Linkvalidator@example.com
        replytoname =
        replytoemail =
        subject = TYPO3 Linkvalidator report
    }
    linkhandler.reportHiddenRecords = 0
}

searchFields for linkvalidator still includes tt_news which results in the following error, while using the linkvalidator check in TYPO3 8.7:

Argument 3 passed to TYPO3\CMS\Core\Database\Query\QueryBuilder::select() must be of the type string, null given, called in [...]/typo3/sysext/linkvalidator/Classes/LinkAnalyzer.php on line 189

I think removing the line tt_news = bodytext,links would be OK, because tx_news is adding their own fields automatically.

Furthermore, when scanning links like http://www.chemmedchem.org/ I get this error:

Call to a member function getStatusCode() on null

Error thrown in file
[...]/typo3/sysext/linkvalidator/Classes/Linktype/ExternalLinktype.php in line 93.

16 TYPO3\CMS\Linkvalidator\Linktype\ExternalLinktype::checkLink("http://www.chemmedchem.org/", array, TYPO3\CMS\Linkvalidator\LinkAnalyzer)