EntityBundleFieldInfoAlterEvent::__construct(): Argument #3 ($bundle) must be of type ?string, int given

Problem/Motivation

A type error occurs when a bundle has a number-only machine name. This is the same issue as #3387995: TypeError: core_event_dispatcher_entity_create_access(): Argument #3 ($entityBundle) must be of type ?string, int given when entity bundle machine namie is number, but in the 4.x version.

Steps to reproduce

Create a node type called '404'.

Proposed resolution

Cast to a string before assigning to the property.