fix: Add backward-compatibility to nc<30

Signed-off-by: Marcel Klehr <mklehr@gmx.net>

lib/Events/AbstractFormEvent.php

@@ -6,21 +6,37 @@
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IWebhookCompatibleEvent;
 
-abstract class AbstractFormEvent extends Event implements IWebhookCompatibleEvent {
-	protected Form $form;
+if (interface_exists(\OCP\EventDispatcher\IWebhookCompatibleEvent::class)) {
+	abstract class AbstractFormEvent extends Event implements IWebhookCompatibleEvent {
+		protected Form $form;
 
-	public function __construct() {
-		parent::__construct();
-	}
+		public function __construct() {
+			parent::__construct();
+		}
+
+		public function getForm(): Form {
+			return $this->form;
+		}
 
-	public function getForm(): Form {
-		return $this->form;
+		/**
+		 * @inheritDoc
+		 */
+		public function getWebhookSerializable(): array {
+			return $this->form->read();
+		}
 	}
 
-	/**
-	 * @inheritDoc
-	 */
-	public function getWebhookSerializable(): array {
-		return $this->form->read();
+} else {
+	// need this block as long as NC < 30 is supported
+	abstract class AbstractFormEvent extends Event {
+		protected Form $form;
+
+		public function __construct() {
+			parent::__construct();
+		}
+
+		public function getForm(): Form {
+			return $this->form;
+		}
 	}
 }