"coverpage candidate  is too small" warnings are spurious

Example:

`2022-06-30 16:04:27,122 INFO      #55219 Job starting for type kindle.images from /Users/Shared/Documents/gitenberg/cache1/epub/55219/pg55219-images.epub
2022-06-30 16:04:27,206 WARNING   #55219 coverpage candidate  is too small (62 x 100)
`

appears after starting the kindle.images job
seems to only happen when ebookconverter is running the job