"Trying to get property of non-object in includes/PageHistory.php on line 257"
Happens because $next === 'unknown', i.e. not an object, on one revision for me with the following fuzz command line test on a local test wiki:
curl --silent --include --globoff -F 'offset'='<<u ' -F 'dir'='prev' 'http://localhost/wiki/index.php?title=Main_Page&action=history' | less
$tools = array();
- if ( !is_null( $next ) ) {
+ if ( !is_null( $next ) && is_object( $next ) ) {
if( $wgUser->isAllowed( 'rollback' ) && $latest ) {
$tools[] = '<span class="mw-rollback-link">'
. $this->mSkin->buildRollbackLink( $rev )