'Cannot read property replace of null' sequelize error

I have a working app perfectly on my local pc with development mode. I switched to heroku, and configured NODE_ENV variable. Somehow it does not work in production mode it is giving me this error:

"atlassian-connect-express": "^6.2.3",
"sequelize": "^6.3.5",
TypeError: Cannot read property 'replace' of null
    at new Sequelize (/app/node_modules/sequelize/lib/sequelize.js:187:43)
    at new SequelizeAdapter (/app/node_modules/atlassian-connect-express/lib/store/sequelize.js:59:33)      
    at module.exports (/app/node_modules/atlassian-connect-express/lib/store/sequelize.js:186:10)
    at Function.stores.create (/app/node_modules/atlassian-connect-express/lib/store/index.js:20:10)        
    at stores (/app/node_modules/atlassian-connect-express/lib/store/index.js:12:17)
    at new Addon (/app/node_modules/atlassian-connect-express/lib/index.js:35:38)
    at module.exports (/app/node_modules/atlassian-connect-express/lib/index.js:231:10)
    at Object.<anonymous> (/app/app.js:57:15)
    at Generator.next (<anonymous>)

sequelize code:

atlassian-connect-express code:

I guess the DB connection URL in your Heroku environment is not as you expect.
Please try logging it out to check if it’s correct.

Hello, can you provide us some source so that we know, how to get this DB Connection URL, or we have to create our own Postgres database and put that URL in the heroku environment?