title: ng build message "ERROR in Cannot read property 'toLowerCase' of undefined"
body: <p>I am using an Azure DevOps YAML pipeline to build/deploy my Angular 9 application.  The YAML contains a Powershell script to build it as follows</p>
  
  <pre><code>- powershell: |
      $angularBuildConfiguration = "MyBuildConfig";
  
      write-host "ng-build start";
      ng build --prod --aot --configuration $angularBuildConfiguration;
      write-host "ng-build end";
  
    workingDirectory: '$(Build.SourcesDirectory)\...'
    displayName: 'Build app - Angular app'
  </code></pre>
  
  <p>The above goes through the Angular build and at the end returns the message "ERROR in Cannot read property 'toLowerCase' of undefined".</p>
  
  <p>I have verified that the workingDirectory and angularBuildConfiguration parameters have the values intended - I have also replaced them with hardcoded values and get the same result.  If I run the Powershell script above on the build server (where the YAML script actually runs on), in the folder intended the build fails with the same error message, however if I build with the same script on my local machine it builds successfully</p>
  
  <p>I don't know whether it is a ng build issue, or whether there is something within my Angular 9 project that causes the error - there is no 'associated' file that is flagged that accompanies the error message</p>
  
  <p>Does anyone have any ideas ?</p>