Fix handling of malformed ActivityPub payloads when URIs are nil (#7370)

* Fix handling of malformed ActivityPub payloads when URIs are nil

* Gracefully handle JSON-LD canonicalization failures

app/services/activitypub/fetch_remote_status_service.rb

@@ -34,6 +34,7 @@ class ActivityPub::FetchRemoteStatusService < BaseService
   end
 
   def trustworthy_attribution?(uri, attributed_to)
+    return false if uri.nil? || attributed_to.nil?
     Addressable::URI.parse(uri).normalized_host.casecmp(Addressable::URI.parse(attributed_to).normalized_host).zero?
   end