Upload of certain bmp files fails, CMS silently skips the uploading of such files

Prerequisite: Build cms 2.20.14-SNAPSHOT, build go green project based on 7.6.6 & CMS 2.20.14-SNAPSHOT and start with cargo.
Steps:
1. Login to CMS, navigate to images folder - upload files of different extensions (gif, jpg, jpeg, bmp, png)
2. All the files are uploaded except bmp with below error message "The uploaded file 'test image23.bmp' has extension bmp which is not allowed. Allowed extensions are: jpg, gif, jpeg, png"
3. Now go to console as admin @ /hippo:configuration/hippo:frontend/cms/cms-services/imageValidationService for property extensions.allowed add *.bmp
4. At CMS, logout & login for configuration to load
5. Again upload files of above extensions

Expected - All the images should be uploaded
Actual - All the images are uploaded except bmp format. This image is silently removed and no error or warning message is shown to the CMS user. Attached exceptions are shown in terminal.
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Note the issue is only on 2.20.xx, coz in 7.8 it displayed below error message
"Upload failed for test image23.bmp.
org.hippoecm.frontend.plugins.gallery.model.GalleryException: Invalid resource: test image23.bmp"