internal error 500 at sending notifications

[juxta73]

Hello, @taqueci

I get error when you send an error notification "internal error 500" (when i make changing settings). Even if the field is empty in the Notification settings. logs do not show an error

Environment:
Redmine version 3.3.1.stable.16111
Ruby version 2.3.3-p222 (2016-11-21) [x86_64-linux]
Rails version 4.2.7.1
Environment production
Database adapter Mysql2
SCM:
Subversion 1.9.3
Git 2.7.4
Filesystem
Redmine plugins:
periodictask 3.1.1
redmine__select2 1.1.0
redmine_banner 0.1.2
redmine_checklists 3.1.5
redmine_ckeditor 1.1.4
redmine_customize 1.2.3
redmine_lightbox2 0.3.1
sidebar_hide 0.0.8