fixed 删除用户时issue，pr用户显示已注销

app/views/api/v1/issues/_detail.json.jbuilder

@@ -27,18 +27,10 @@ json.milestone do
   end
 end
 json.author do
-  if issue.user.present? 
-    json.partial! "api/v1/users/simple_user", locals: {user: issue.user}
-  else 
-    json.nil! 
-  end
+  json.partial! "api/v1/users/simple_user", locals: {user: issue.user}
 end
 json.changer do 
-  if issue.changer.present? 
-    json.partial! "api/v1/users/simple_user", locals: {user: issue.changer}
-  else 
-    json.nil! 
-  end
+  json.partial! "api/v1/users/simple_user", locals: {user: issue.changer}
 end
 json.assigners issue.show_assigners.each do |assigner| 
   json.partial! "api/v1/users/simple_user", locals: {user: assigner}

app/views/api/v1/users/_simple_user.json.jbuilder

@@ -4,6 +4,7 @@ if user.present?
   json.name user.real_name
   json.login user.login
   json.image_url Rails.application.config_for(:configuration)['platform_url'] + "/" + url_to_avatar(user).to_s
-else 
-  json.nil!
+else
+  json.name "已注销"
+  json.login ""
 end