Fix BootstrapTimelineService crashing when bootstrapped accounts are invalid (#12037)

* Add test to handle suspended and missing users in BootstrapTimelineService

* Fix BootstrapTimelineService crashing when bootstrapped accounts are invalid

spec/services/bootstrap_timeline_service_spec.rb

@@ -22,9 +22,10 @@ RSpec.describe BootstrapTimelineService, type: :service do
     context 'when setting is set' do
       let!(:alice) { Fabricate(:account, username: 'alice') }
       let!(:bob)   { Fabricate(:account, username: 'bob') }
+      let!(:eve)   { Fabricate(:account, username: 'eve', suspended: true) }
 
       before do
-        Setting.bootstrap_timeline_accounts = 'alice, bob'
+        Setting.bootstrap_timeline_accounts = 'alice, @bob, eve, unknown'
         subject.call(source_account)
       end
 
@@ -32,6 +33,10 @@ RSpec.describe BootstrapTimelineService, type: :service do
         expect(source_account.following?(alice)).to be true
         expect(source_account.following?(bob)).to be true
       end
+
+      it 'does not follow suspended account' do
+        expect(source_account.following?(eve)).to be false
+      end
     end
   end
 end