Error messages are not cleared when uploading invalid images at different image variants in gallery editor mode

If uploading two invalid images at different variants, there are two error messages displayed while the expectation is to show only the last error message.

Reproduction path:

1. Edit an image
2. In the first variant (e.g. thumbnail), select and upload a "too wide/high" image (>1920x1080). Expect to see the message: "The image ... is too wide/high..."
3. In another variant (e.g. mobile), select and upload a "too large" image (>4MB).
   • Expected: the previous message is removed. The new error message is displayed.
   • Actual: second message is display beside the first one: "The file ... is ... MB which is too large".
4. It's the same when uploading invalid images to other variants.
5. Return to the first variant, upload the new valid image.
   • Expected: all error messages are cleared.
   • Actual: The first message is cleared, but other error messages are still there. It's impossible to save and close the document because of error messages in the feedback.