Debido a los problemas de implementación de bloqueo, MySQL no permite referenciar la tabla afectada con DELETE o UPDATE .
Necesitas hacer un JOIN aquí en cambio:
DELETE gc.*
FROM guide_category AS gc
LEFT JOIN
guide AS g
ON g.id_guide = gc.id_guide
WHERE g.title IS NULL
o simplemente use un NOT IN :
DELETE
FROM guide_category AS gc
WHERE id_guide NOT IN
(
SELECT id_guide
FROM guide
)