[API] Fix creating issue when assignee_id is empty

see https://gitlab.com/gitlab-org/gitlab-ce/issues/42025

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/api/helpers/common_helpers.rb b/lib/api/helpers/common_helpers.rb
index 322624c6092..9993caa5249 100644
--- a/lib/api/helpers/common_helpers.rb
+++ b/lib/api/helpers/common_helpers.rb
@@ -3,8 +3,10 @@ module API
     module CommonHelpers
       def convert_parameters_from_legacy_format(params)
         params.tap do |params|
-          if params[:assignee_id].present?
-            params[:assignee_ids] = [params.delete(:assignee_id)]
+          assignee_id = params.delete(:assignee_id)
+
+          if assignee_id.present?
+            params[:assignee_ids] = [assignee_id]
           end
         end
       end