Error on node preview without saving the node

Problem/Motivation

Problem description: when I create a new node and add the Instagram field value and then click the "preview" button without saving the node, I receive the error:

"The website encountered an unexpected error. Please try again later.
Error: Call to a member function mainPropertyName() on null in Drupal\media_entity_instagram\Plugin\media\Source\Instagram->matchRegexp() (line 237 of modules/contrib/media_entity_instagram/src/Plugin/media/Source/Instagram.php)."

Proposed resolution

Currently I have no solution how to resolve it.

Remaining tasks

Fix needed, reviews needed, tests to be written or run

User interface changes

No user interface changes required.

I'm using Drupal 8.8..x