Redmine got 500 error after installed this plugin

[arkhitech]

Redmine got 500 error after installed this plugin

[galexrt]

I'm getting the same error as @rikki I'm using the same version of redmine and ruby as him

Processing by IssuesController#new as HTML
  Parameters: {"project_id"=>"iito-hso-mgmt-dm"}
  Current user: Galexrt (id=3)
  Rendered issues/_form_custom_fields.html.erb (4.4ms)
  Rendered issues/_attributes.html.erb (21.8ms)
  Rendered plugins/redmine_mentions/app/views/hooks/redmine_mentions/_edit_mentionable.html.erb (3.3ms)
  Rendered issues/_form.html.erb (36.6ms)
  Rendered issues/new.html.erb within layouts/base (38.0ms)
Completed 500 Internal Server Error in 66ms

ActionView::Template::Error (undefined method `delete_if' for #<User::ActiveRecord_Relation:0x007f9318039550>):
    4: <% regex_find = '/\B'+Setting.plugin_redmine_mentions['trigger']+'(\w*)$/i'%>
    5:
    6:
    7: <%users= @project.users.delete_if{|u| (u.type != 'User' || u.mail.empty?)}%>
    8: <%users_regex=users.collect{|u| "#{Setting.plugin_redmine_mentions['trigger']}#{u.login}"}.join('|')%>
    9: <% regex_highlight = '/\B('+users_regex+')/g' %>
   10: <script>
  lib/redmine/hook.rb:120:in `block (2 levels) in render_on'
  lib/redmine/hook.rb:118:in `map'
  lib/redmine/hook.rb:118:in `block in render_on'
  lib/redmine/hook.rb:62:in `block (2 levels) in call_hook'
  lib/redmine/hook.rb:62:in `each'
  lib/redmine/hook.rb:62:in `block in call_hook'
  lib/redmine/hook.rb:59:in `tap'
  lib/redmine/hook.rb:59:in `call_hook'
  lib/redmine/hook.rb:168:in `call_hook'
  app/views/issues/_form.html.erb:44:in `block in _app_views_issues__form_html_erb__1231411727637894253_70134883614000'
  app/helpers/application_helper.rb:1024:in `labelled_fields_for'
  app/views/issues/_form.html.erb:1:in `_app_views_issues__form_html_erb__1231411727637894253_70134883614000'
  app/views/issues/new.html.erb:11:in `block in _app_views_issues_new_html_erb__2465577942882988662_70134881425360'
  app/helpers/application_helper.rb:1017:in `labelled_form_for'
  app/views/issues/new.html.erb:5:in `_app_views_issues_new_html_erb__2465577942882988662_70134881425360'
  app/controllers/issues_controller.rb:144:in `block (2 levels) in new'
  app/controllers/issues_controller.rb:143:in `new'

For now I deactivated the plugin to being able to create issues, but I hope this being fixed fast. 😃

[zohar]

Same error here. redmine 2.2.1

Note the errors at the end:

Started PUT "//issues/38402" for 33.41.33.41 at Mon Aug 03 13:45:58 +0300 2015
Processing by IssuesController#update as HTML
  Parameters: {"issue"=>{"parent_issue_id"=>"", "done_ratio"=>"0", "priority_id"=>"4", "start_date"=>"2015-08-03 00:00:00", "notes"=>"Looking in logs (@username )", "assigned_to_id"=>"", "tracker_id"=>"4", "description"=>"@otheruser did you receive any mail/notification?", "fixed_version_id"=>"", "private_notes"=>"0", "subject"=>"Testing mentions", "lock_version"=>"3", "is_private"=>"0", "status_id"=>"1", "due_date"=>"", "estimated_hours"=>"", "project_id"=>"00000"}, "commit"=>"Submit", "time_entry"=>{"comments"=>"", "hours"=>"", "activity_id"=>"9"}, "utf8"=>"✓", "attachments"=>{"1"=>{"description"=>""}}, "id"=>"38402", "last_journal_id"=>"94418", "authenticity_token"=>"xxxxxxx"}
  Current user: username (id=4)
Completed 500 Internal Server Error in 416ms

SyntaxError (/usr/local/redmine-2.2.1/plugins/redmine_mentions/app/models/mention_mailer.rb:3: syntax error, unexpected ':', expecting kEND
  default from: Setting.mail_from
               ^
/usr/local/redmine-2.2.1/plugins/redmine_mentions/app/models/mention_mailer.rb:12: syntax error, unexpected ':', expecting ')'
    mail(to: user.mail, subject: "[#{@issu...
            ^
/usr/local/redmine-2.2.1/plugins/redmine_mentions/app/models/mention_mailer.rb:12: syntax error, unexpected ':', expecting '='
...  mail(to: user.mail, subject: "[#{@issue.tracker.name} ##{@...
                              ^
/usr/local/redmine-2.2.1/plugins/redmine_mentions/app/models/mention_mailer.rb:12: syntax error, unexpected ')', expecting kEND):
  app/models/journal.rb:52:in `save'
  app/models/issue.rb:1362:in `create_journal'
  app/models/issue.rb:965:in `save_issue_with_child_records'
  app/models/issue.rb:952:in `save_issue_with_child_records'
  app/controllers/issues_controller.rb:176:in `update'