It's another way of saying "De nada" ("You're welcome"). It is quite common in Spain.

-No hay de que, abreviatura de (no hay de que agradecer). Similar to You are welcome. De nada: You are welcome

In Spanish we have different ways to answer when someone says, "Gracias" some of these expressions are more common in one country than in others. “No hay de qué” It is one of those expressions. example: Persona 1: Gracias (Thank you) Persona 2: No hay de qué (you are welcome / don’t mention it!) Other ways to respond when someone says “Gracias” are: De nada: literally means “For nothing” Por nada: literally means “For nothing” A la orden. Is like “I am at your disposal”