FIX: anonymized user's preferences should have system assigned avatar chosen

app/services/user_anonymizer.rb

@@ -28,6 +28,7 @@ class UserAnonymizer
       @user.email_direct = false
       @user.email_always = false
       @user.mailing_list_mode = false
+      @user.uploaded_avatar_id = nil
       @user.save
 
       profile = @user.user_profile

spec/services/user_anonymizer_spec.rb

@@ -59,10 +59,12 @@ describe UserAnonymizer do
     it "removes the avatar" do
       upload = Fabricate(:upload, user: user)
       user.user_avatar = UserAvatar.new(user_id: user.id, custom_upload_id: upload.id)
+      user.uploaded_avatar_id = upload.id # chosen in user preferences
       user.save!
       expect { make_anonymous }.to change { Upload.count }.by(-1)
       user.reload
       expect(user.user_avatar).to eq(nil)
+      expect(user.uploaded_avatar_id).to eq(nil)
     end
 
     it "logs the action" do