Wrap MemberPresenter#attending_workshops safely

This now checks if the object passed to the Presenter is `nil` and responds accordingly. I've updated the logic in the dashboard_controller.rb to reflect the change

Signed-off-by: jonathan.kerr <3410350+jonodrew@users.noreply.github.com>

Author: jonodrew

app/controllers/dashboard_controller.rb

@@ -4,16 +4,16 @@ class DashboardController < ApplicationController
 
   DEFAULT_UPCOMING_EVENTS = 5
 
-  helper_method :year_param, :attending_workshops
+  helper_method :year_param
 
   def show
     @chapters = Chapter.active.all.order(:created_at)
-    @user = current_user ? MemberPresenter.new(current_user) : nil
+    @user = MemberPresenter.new(current_user)
     @upcoming_workshops = upcoming_events.map.inject({}) do |hash, (key, value)|
       hash[key] = EventPresenter.decorate_collection(value)
       hash
     end
-    @attending_ids = attending_workshops
+    @attending_ids = @user.attending_workshops
     @testimonials = Testimonial.order(Arel.sql('RANDOM()')).limit(5).includes(:member)
   end
 
@@ -84,8 +84,4 @@ def all_events(workshops)
 
     [*workshops, *events, meeting].uniq.compact
   end
-
-  def attending_workshops
-    current_user.nil? ? Set.new : current_user.workshop_invitations.accepted.pluck(:id).to_set
-  end
 end

app/presenters/member_presenter.rb

@@ -1,4 +1,9 @@
 class MemberPresenter < BasePresenter
+
+  def initialize(current_user)
+    @member = current_user
+    super
+  end
   def organiser?
     has_role? :organiser, :any
   end
@@ -23,6 +28,10 @@ def pairing_details_array(role, tutorial, note)
     role.eql?('Coach') ? coach_pairing_details(note) : student_pairing_details(tutorial, note)
   end
 
+  def attending_workshops
+    @member.nil? ? Set.new : workshop_invitations.accepted.pluck(:id).to_set
+  end
+
   private
 
   def coach_pairing_details(note)