Fix crash when processing Flag activity with no status (#26189)

app/lib/activitypub/activity/flag.rb

@@ -9,7 +9,7 @@ class ActivityPub::Activity::Flag < ActivityPub::Activity
 
     target_accounts.each do |target_account|
       target_statuses     = target_statuses_by_account[target_account.id]
-      replied_to_accounts = Account.local.where(id: target_statuses.filter_map(&:in_reply_to_account_id))
+      replied_to_accounts = target_statuses.nil? ? [] : Account.local.where(id: target_statuses.filter_map(&:in_reply_to_account_id))
 
       next if target_account.suspended? || (!target_account.local? && replied_to_accounts.none?)
 

spec/lib/activitypub/activity/flag_spec.rb

@@ -139,6 +139,35 @@ RSpec.describe ActivityPub::Activity::Flag do
         expect(report.status_ids).to eq []
       end
     end
+
+    context 'when an account is passed but no status' do
+      let(:mentioned) { Fabricate(:account) }
+
+      let(:json) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          id: flag_id,
+          type: 'Flag',
+          content: 'Boo!!',
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: [
+            ActivityPub::TagManager.instance.uri_for(flagged),
+          ],
+        }.with_indifferent_access
+      end
+
+      before do
+        subject.perform
+      end
+
+      it 'creates a report with no attached status' do
+        report = Report.find_by(account: sender, target_account: flagged)
+
+        expect(report).to_not be_nil
+        expect(report.comment).to eq 'Boo!!'
+        expect(report.status_ids).to eq []
+      end
+    end
   end
 
   describe '#perform with a defined uri' do