Observed at translatewiki.net: PHP Fatal error: Call to a member function isError() on a non-object in /www/translatewiki.net/w/includes/filerepo/file/File.php on line 907

Code snippet:

$thumb = $this->transform( $params );
if ( is_null( $thumb ) || $thumb->isError() ) {
    return '';
}

Happens when $thumb is false, which means that $thumb->isError() is called on a non-object.

Version: unspecified
Severity: normal