Im::isAllowDeleteFolder

public function isAllowDeleteFolder(DiskFolder $folder): bool
{
	if ($folder->isDeleted())
	{
		return true;
	}

	static $imStorageId;
	if (empty($imStorageId))
	{
		$storageList = $this->getStorageList();
		if ($storageList[0] instanceof DiskStorage)
		{
			$imStorageId = $storageList[0]->getId();
		}
	}

	// disallow drop any folders within IM storage
	return (bool)($imStorageId != $folder->getStorageId());
}