From 1.27.0 it may not be ideal to use unset unset( $wgFooterIcons['copyright'] );
to disable CopyrightIcon. It may cause PHP Notice: Undefined index: copyright in /usr/share/webapps/mediawiki/includes/skins/Skin.php on line 783.
Workaround: Do not unset $wgFooterIcons['copyright'], leave it as it is.
Set $wgRightsIcon to null value (default).