Found Error "Missing open office binary that is mandatory for conversion." After integrate Documents feature

After install owncloud 9.1 and install libreoffice 5.2
config php file in this below

$CONFIG = array (
'updatechecker' => false,
'instanceid' => 'oc0gymn78hji',
'preview_libreoffice_path' => '/opt/libreoffice5.2',
'preview_office_cl_parameters' =>
' --headless --nologo --nofirststartwizard --invisible --norestore '.
'-convert-to pdf -outdir ',

Please suggestion or any comment.

This is a folder, but you need to specify the binary here. Also remove the 'preview_office_cl_parameters' from your config.php