Merge pull request #44178 from nextcloud/fix/noid/nav-init-add

fix(Navigation): ensure NavManager is inited when adding an entry

lib/private/NavigationManager.php

 			$this->closureEntries[] = $entry;
 			return;
 		}
+		$this->init();
 
 		$id = $entry['id'];
 
 			]);
 		}
 
-		if ($this->appManager === 'null') {
-			return;
-		}
-
 		$this->defaultApp = $this->appManager->getDefaultAppForUser($this->userSession->getUser(), false);
 
 		if ($this->userSession->isLoggedIn()) {