Deleting nonexistent user email via API causes internal server error

[matusf]

• Gitea version (or commit ref): Gitea version 1.13.7 built with GNU Make 4.1, go1.15.11 : bindata, sqlite, sqlite_unlock_notify
• Git version: git version 2.17.
• Operating system: Ubuntu 18.04
• Downloaded gitea from downloads page
• Running as a command-line program
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
• Log gist:

2021/04/09 01:45:57 Started DELETE /api/v1/user/emails for 127.0.0.1
2021/04/09 01:45:57 ...api/v1/user/email.go:128:DeleteEmail() [E] DeleteEmailAddresses: Email address does not exist
2021/04/09 01:45:57 Completed DELETE /api/v1/user/emails 500 Internal Server Error in 50.684576ms

Description

Make a DELETE request on /user/emails endpoint with supplied authorization token and invalid email in the body. Then 500 response is returned with following response body:

curl -v -X DELETE -H "Authorization: token $TOKEN" -d '{"emails":["xxx",""]}' 'http://localhost:2999/api/v1/user/emails' -H "Content-Type: application/json"
{"message":"","url":"http://localhost:3000/api/swagger"}