permissionsdao: no silent fallback to user-permissions if we find none for user

database/permissionsdao.h

@@ -6,7 +6,7 @@ class PermissionsDao
 {
   public:
 	PermissionsDao();
-	virtual Permissions find(std::string pagename, std::string username) = 0;
+	virtual std::optional<Permissions> find(std::string pagename, std::string username) = 0;
 };
 
 #endif // PERMISSIONSDAO_H