Be more robust against failures when trying to get the owner of the share we are trying to mount

If we fail to get the owner of the view from the cache,
e.g. because the user never logged in but a cron job runs
We fallback to calculating the owner from the root of the view:

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/Share/Listener.php

@@ -79,7 +79,23 @@ class Listener {
 		}
 
 		if ($event->getParent() === RoomShareProvider::TALK_FOLDER_PLACEHOLDER) {
-			$parent = $this->config->getAttachmentFolder($view->getOwner('/'));
+			try {
+				$userId = $view->getOwner('/');
+			} catch (\Exception $e) {
+				// If we fail to get the owner of the view from the cache,
+				// e.g. because the user never logged in but a cron job runs
+				// We fallback to calculating the owner from the root of the view:
+				if (substr_count($view->getRoot(), '/') >= 2) {
+					// /37c09aa0-1b92-4cf6-8c66-86d8cac8c1d0/files
+					[, $userId, ] = explode('/', $view->getRoot(), 3);
+				} else {
+					// Something weird is going on, we can't fallback more
+					// so for now we don't overwrite the share path ¯\_(ツ)_/¯
+					return;
+				}
+			}
+
+			$parent = $this->config->getAttachmentFolder($userId);
 			$event->setParent($parent);
 			if (!$event->getView()->is_dir($parent)) {
 				$event->getView()->mkdir($parent);