Changing machine name of image style leads to WSOD when loading widgets that used the old name

Problem/Motivation

The standard profile ships with some image styles (thumbnail, medium and large) that are used in other config entities shipped by the profile.

However, it is possible to edit the image style and modify its machine name. When this happens, the form displays that use that image style are not updated correctly, which leads to a WSOD when the widget tries to use the non-existent value.

Steps to reproduce
1) Install the standard profile
2) Create a node of the "Article" content type, uploading an image to the image field.
3) Go to /admin/config/media/image-styles
4) Edit the "Thumbnail" image style, changing its machine name to something else
5) Edit the node you created in step 2, and experience the WSOD

Proposed resolution

1) Fix the bug by updating the form displays when an image display has its machine name modified.

Remaining tasks

User interface changes

API changes

Data model changes

========== Original issue report by @desierto ==============

(Debian 8, Apache 2.4, Maria DB 5.5.60, PHP 5.6.33)

To reproduce the issue:

• Install default Drupal 8 with composer
• Enable media module
• Create/upload a media image
• Edit the name and Machine name of the default Thumbnail image style and save
• Go the the /admin/content/media page or try to edit the created media image and you will get a 500 error or white screen

Also it throws an error if you try to add a new media image... it will let you pick an image, but will not finish the attachment of the image and you will be unable to save a new image media.

Another note is that the media image type is not even configured to use the thumbnail image style.

To fix I have tried to flush the thumbnail image style, run cron, clear all caches, and run update.php. So far nothing has helped, including trying to create a new image style and delete all the others, choosing the new style as the replacement style. On another website I even tried delete the media image type altogether and recreating (w/o changing styles again) a new media image type. The errors persist.

There are no errors in Drupal error logs. Apache's error logs show these errors:

PHP Fatal error: Call to a member function getCacheTags() on null in /www/test2/web/core/modules/image/src/Plugin/Field/FieldFormatter/ImageFormatter.php on line 199

PHP Fatal error: Call to a member function transformDimensions() on null in /www/test2/web/core/modules/image/image.module on line 298

Should one not be allowed to change the image style machine name (I'm assuming that's where the problem lies) once media is created? Thanks for any ideas or fixes.