Fix status processing failing halfway when a remote post has a malfor…

…med `replies` attribute (mastodon#31246)

app/lib/activitypub/activity/create.rb

@@ -336,13 +336,15 @@ def resolve_thread(status)
 
   def fetch_replies(status)
     collection = @object['replies']
-    return if collection.nil?
+    return if collection.blank?
 
     replies = ActivityPub::FetchRepliesService.new.call(status, collection, allow_synchronous_requests: false, request_id: @options[:request_id])
     return unless replies.nil?
 
     uri = value_or_id(collection)
     ActivityPub::FetchRepliesWorker.perform_async(status.id, uri, { 'request_id' => @options[:request_id] }) unless uri.nil?
+  rescue => e
+    Rails.logger.warn "Error fetching replies: #{e}"
   end
 
   def conversation_from_uri(uri)