Image information is empty on defaultimageresizemethod admin setting change

[golenkovm]

Describe the bug When testing a patch for https://github.com/gjbarnard/moodle-format_grid/issues/211 it's been found that in some sites we are getting the "Image information is empty" error:

After removing the image from Moodle the admin setting change exploded on another image but with the same error.

To Reproduce Steps to reproduce the behaviour:

1. Go to admin page and change defaultimageresizemethod to any value
2. Click on Save
3. See error

Expected behaviour Admin setting should be saved with no error displayed

Versions (please complete the following information):

• Moodle: 4.1
• Format: https://github.com/gjbarnard/moodle-format_grid/tree/909cafcbc351c52d4dc5d4af535c3f76d8dec5d4