duplicateApp function Null safety

FirebaseException duplicateApp(
  1. String appName
)

Throws a consistent cross-platform error message when an app is being created which already exists.

Implementation

FirebaseException duplicateApp(String appName) {
  return FirebaseException(
      plugin: 'core',
      code: 'duplicate-app',
      message: 'A Firebase App named "$appName" already exists');
}