competition: fix

app/services/competitions/join_team_service.rb

@@ -32,6 +32,6 @@ class Competitions::JoinTeamService < ApplicationService
     raise Error, '该战队队员人数已满' if !is_teacher && team.members.count == competition.member_staff.maximum
 
     role = is_teacher ? 3 : 2
-    team.team_members.create!(competition_id: competition.id, user_id: user, role: role, is_teacher: is_teacher)
+    team.team_members.create!(competition_id: competition.id, user_id: user.id, role: role, is_teacher: is_teacher)
   end
 end