Fatal error when no drupal/core package is present

[T2L]

When no drupal/core package is present running most of composer commands raises an exception

Script DrupalComposer\DrupalScaffold\Plugin::scaffold handling the post-update-cmd event terminated with an exception


  [ErrorException]
  Argument 1 passed to Composer\Installer\InstallationManager::getInstallPath() must implement interface Composer\Package\PackageInterface, null given, called in .../drupal-scaffold/src/Handler.php on line 224 and defined

[T2L]

See pull request #56