fix(ui): correctly fallback to error message when traceback is empty string

Author: psychedelicious

invokeai/frontend/web/src/features/queue/components/QueueList/QueueItemDetail.tsx

@@ -89,7 +89,7 @@ const QueueItemComponent = ({ queueItemDTO }: Props) => {
           <Heading size="sm" color="error.400">
             {t('common.error')}
           </Heading>
-          <pre>{queueItem?.error_traceback ?? queueItem?.error_message}</pre>
+          <pre>{queueItem?.error_traceback || queueItem?.error_message}</pre>
         </Flex>
       )}
       <Flex layerStyle="second" h={512} w="full" borderRadius="base" alignItems="center" justifyContent="center">