fix: no method error when conversation is nil (#7566)

enterprise/lib/enterprise/integrations/openai_processor_service.rb

@@ -23,14 +23,17 @@ module Enterprise::Integrations::OpenaiProcessorService
   end
 
   def labels_with_messages
-    labels = hook.account.labels.pluck(:title).join(', ')
-
-    character_count = labels.length
     conversation = find_conversation
 
+    # return nil if conversation is not present
+    return nil if conversation.nil?
+
     # return nil if conversation has less than 3 incoming messages
     return nil if conversation.messages.incoming.count < 3
 
+    labels = hook.account.labels.pluck(:title).join(', ')
+    character_count = labels.length
+
     messages = init_messages_body(false)
     add_messages_until_token_limit(conversation, messages, false, character_count)