No check for empty file upload in common/src/file-upload.controller.ts

[gnaaruag]

Currently in common/src/file-upload.controller.ts empty file uploads are allowed to be uploaded. Proposed PR adds a check before letting the upload take place.

This ticket helps with the following aspect

• Potential resource efficiency
• potential security gains (to prevent a mass empty file upload exploit)
• Only valid files pass through (improves data integrity)