TYPO3 Core

htmlspecialchars() expects parameter 1 to be string, null given TypeError thrown in file /usr/local/share/typo3/typo3_src-8.7.8/typo3/sysext/rte_ckeditor/Classes/Controller/BrowseLinksController.php in line 387.

Reproduce:

• Activate relAttribute in ckeditor configuration with
  

  buttons:
    link:
      relAttribute:
        enabled: true
  

• Set a link in ckeditor
• click on the link button again

Change

        $currentRel = $this->displayedLinkHandler === $this->currentLinkHandler && !empty($this->currentLinkParts)
            ? $this->linkAttributeValues['rel']
            : '';

to

        $currentRel = $this->displayedLinkHandler === $this->currentLinkHandler && !empty($this->currentLinkParts) && !is_null($this->linkAttributeValues['rel'])
            ? $this->linkAttributeValues['rel']
            : '';

in line 376