Cannot read property 'categories' of null

Cannot read property 'categories' of null

          
              TypeError: Cannot read property 'categories' of null
    at postController.single (C:\inetpub\wwwroot-iranbinary\app\http\controllers\postController.js:90:59)
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)