更改：禅道脚本中数据为空处理

lib/tasks/import_issues_from_chandao.rake

@@ -12,7 +12,9 @@ namespace :import_from_chandao do
       author = User.like(randd_field_hash['由谁创建']).take
       issue.author_id = author&.id 
       assigner = User.like(randd_field_hash['指派给']).take 
-      issue.assigners << assigner
+      if assigner.present? 
+        issue.assigners << assigner
+      end
       issue.status_id = IssueStatus.first.id
       issue.tracker_id = Tracker.first.id
       issue.priority_id = randd_field_hash['优先级'].to_i
@@ -37,7 +39,9 @@ namespace :import_from_chandao do
       author = User.like(randd_field_hash['由谁创建']).take
       issue.author_id = author&.id 
       assigner = User.like(randd_field_hash['指派给']).take 
-      issue.assigners << assigner
+      if assigner.present? 
+        issue.assigners << assigner
+      end
       issue.status_id = IssueStatus.first.id
       issue.tracker_id = Tracker.first.id
       issue.priority_id = randd_field_hash['优先级'].to_i