Invalid argument supplied for foreach()

Warning: Invalid argument supplied for foreach() in /home/dnk/public_html/ ****/wp-includes/post.php on line 1215

foreach ( $capabilities as $core => $custom ) {
if ( in_array( $core, array( ‘read_post’, ‘delete_post’, ‘edit_post’ ) ) ) {
$post_type_meta_caps[ $custom ] = $core;