http 500 error after upgrade wordpress

Dear All,

please help for my error, after upgrade the wordpress version

PHP Warning: Invalid argument supplied for foreach() in /home/nuruzorg/public_html/wp-includes/plugin.php on line 678
[02-May-2016 03:27:24 UTC] PHP Fatal error: Class ‘WP_Widget’ not found in /home/nuruzorg/public_html/wp-includes/widgets/class-wp-widget-pages.php on line 17

foreach ( $wp_plugin_paths as $dir => $realdir ) {
if ( strpos( $file, $realdir ) === 0 ) {
$file = $dir . substr( $file, strlen( $realdir ) );
}
}

Need your Help please

THanks
NAP