Fix Composer usage

Fixes #441

inc/composer/class-plugin.php

@@ -121,7 +121,7 @@ public function pre_operations_exec( InstallerEvent $event ) : void {
 	 */
 	protected function resolve_packages_composer_v2( array $packages, array $operations ) : array {
 		foreach ( $operations as $operation ) {
-			switch ( $operation::TYPE ) {
+			switch ( $operation->getOperationType() ) {
 				case 'install':
 				case 'markAliasInstalled':
 					$package = $operation->getPackage();