HideImageForm: add tests

The puzzle `1383-68064f45` from #1383 has to be resolved: 

https://github.com/php-coder/mystamps/blob/2305f073ceef77c962f330629b73c32cf4c6cc54/src/main/frontend/src/components/HideImageForm.js#L7-L7

The puzzle was created by Slava Semushin on 07-Feb-21.
