blueimp/jQuery-File-Upload — pull request #3323 by DerDu (2014-08-28 11:16:43+00:00)
Title: Proxy/Balancer: HTTPS was not recognized

Fix for #3322

Request -- (https) --> Balancer -- (http) --> Worker

Then the following isn't available with the worker: $_SERVER['HTTPS'] == 'on'
So.. delete link will be always http, you also have to check: $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https'