Queries :: How To Properly Use IsError In Query

I want this query to count all of the different types of order (Clase de Orden) and if a type of order isn't found, to return zero. How do I do this using IsError, since when it doesn't find an order, it gives me an error. This is the query:

TRANSFORM Count([E 025].Porcin) AS CountOfPorcin
SELECT[Listado de Empleados].Supervisor, [E 025].[Alias de TP], [E 025].Usuario, Telfonos.Telefono, Count([E 025].Porcin) AS [Total Of Porcin]
FROM Telfonos INNER JOIN ([Listado de Empleados] INNER JOIN [E 025] ON[Listado de Empleados].[Codigo de Usuario] = [E 025].Usuario) ON

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