I'm getting the following error message when ng build --prod :

Environment
Angular version: 6.1.4
Version of @techiediaries/ngx-qrcode:
"@techiediaries/ngx-qrcode": "9.1.0",
For Tooling issues:
- Node version: 10.15.3
- Platform: Windows
Others:
"devDependencies": {
"@angular-devkit/build-angular": "~0.7.4",
"@angular-devkit/build-ng-packagr": "~0.7.4",
"@angular-devkit/core": "0.4.2",
"@angular-devkit/schematics": "0.4.2",
"@angular/cli": "^6.1.5",
"@angular/compiler-cli": "6.1.4",
"@angular/language-service": "6.1.4",
Thank you for your help