parentJsonpFunction is not a function at webpackJsonpCallback error getting while integrating in angular 8

[linoymohan]

Getting below error when integrating chat21 widget in angular 7 and 8 .

Uncaught TypeError: parentJsonpFunction is not a function
at webpackJsonpCallback (inline.bundle.js:20)
at polyfills.bundle.js:1

chat21 is angular 5 project
so i think webpack version mismatch is the problem .
kindly help to fix this