fix competition join team

app/controllers/competition_teams_controller.rb

@@ -145,7 +145,7 @@ class CompetitionTeamsController < ApplicationController
 
     # 老师身份加入战队
     if User.current.user_extensions.identity == 0
-      teacher_staff = @competition.where(category: 'teacher').first
+      teacher_staff = @competition.competition_staffs.where(category: 'teacher').first
 
       if teacher_staff.blank?
         @status, @message = -1, '该竞赛不能配备导师'
@@ -158,7 +158,7 @@ class CompetitionTeamsController < ApplicationController
       end
       team.team_members.create!(user_id: User.current.id, role: 3, competition_id: @competition.id, is_teacher: true)
     else
-      max_member_count = @competition.where('category != "teacher"').sum(:maximum)
+      max_member_count = @competition.competition_staffs.where('category != "teacher"').sum(:maximum)
       if team.members.count + 1 > max_member_count
         @status, @message = -1, '该战队成员人数已满'
         return