List tables: Better primary column back-compat.

Why are people manually setting `$_column_headers` other than because somebody else told them to? Maybe time will tell.

props kovshenin.
see #25408.

Built from https://develop.svn.wordpress.org/trunk@32722


git-svn-id: http://core.svn.wordpress.org/trunk@32692 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-list-table.php

@@ -850,8 +850,16 @@ class WP_List_Table {
 	 * @return array
 	 */
 	protected function get_column_info() {
-		if ( isset( $this->_column_headers ) && is_array( $this->_column_headers ) && count( $this->_column_headers ) >= 4 ) {
-			return $this->_column_headers;
+		// $_column_headers is already set / cached
+		if ( isset( $this->_column_headers ) && is_array( $this->_column_headers ) ) {
+			// Back-compat for list tables that have been manually setting $_column_headers for horse reasons.
+			// In 4.3, we added a fourth argument for primary column.
+			$column_headers = array( array(), array(), array(), '' );
+			foreach ( $this->_column_headers as $key => $value ) {
+				$column_headers[ $key ] = $value;
+			}
+
+			return $column_headers;
 		}
 
 		$columns = get_column_headers( $this->screen );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.3-alpha-32721';
+$wp_version = '4.3-alpha-32722';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.