Scheduler breaks ajax requests when content moderation is enabled

Problem

When creating a new moderated content (node) with scheduler enabled for that content content type, when I try to add multiple medias it breaks the ajax request and when I checked the logs I got the following error:
InvalidArgumentException: The state '' does not exist in workflow

Proposed resolution

The issue seems to be in function _scheduler_content_moderation_integration_states_values when trying to grab the current state. In some situations the moderation state is null, and therefore we should use the default one.