TypeCannot read property 'leftNumber' of null

Error: TypeError: Cannot read property 'leftNumber' of null
    at /home/ubuntu/website/www.mclouds.io/node/server/build/webpack:/assets/pages/ProductDetail.js:12:19
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)