fix: fallback deletion url to relative path

if homeDomain is not configured via config file or env var

the deletion url is a frontend page, so it cannot simply assume it's on
the same domain as uploaded files

controllers/uploadController.js

@@ -1103,7 +1103,7 @@ self.sendUploadResponse = async (req, res, result) => {
       // If uploaded by user, add delete URL (intended for ShareX and its derivatives)
       // Homepage uploader will not use this (use dashboard instead)
       if (req.locals.user) {
-        map.deleteUrl = `${utils.conf.homeDomain}/file/${file.name}?delete`
+        map.deleteUrl = `${utils.conf.homeDomain || ''}/file/${file.name}?delete`
       }
 
       return map