Index: src/wp-admin/includes/class-wp-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-list-table.php	(revision 32712)
+++ src/wp-admin/includes/class-wp-list-table.php	(working copy)
@@ -850,8 +850,9 @@
 	 * @return array
 	 */
 	protected function get_column_info() {
-		if ( isset( $this->_column_headers ) )
+		if ( isset( $this->_column_headers ) && is_array( $this->_column_headers ) && 4 === count( $this->_column_headers ) ) {
 			return $this->_column_headers;
+		}
 
 		$columns = get_column_headers( $this->screen );
 		$hidden = get_hidden_columns( $this->screen );