File upload validation

When I submit the form without selecting a file, I get this HTML doctype response titled with: ‘Cannot validate mimtype for a missing file’. Instead of getting error validation message.
Any clarification & thanks in advance.

Can you please show your input form?

I use fetch api to send the request and intercept response to check validation errors, the other validation checks like mimeType, fileSize, and extensions work well

Problem solved, it was FormData.append() setting the photo value as undefined when no file is selected. Thanks.